


Something in Return

by SewerWitch



Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Age Difference, Anal Fingering, Anal Sex, Bathroom Sex, Blow Jobs, Bottom!Senku, Cybersex, Discord: The Kingdom of Shipping (Dr. STONE), Eventual Sex, M/M, Mutual Masturbation, Phone Sex, Public Sex, Rimming, Spoilers, Teacher-Student Relationship, Two Shot, top!xeno
Language: English
Status: In-Progress
Published: 2020-06-29
Updated: 2020-07-11
Packaged: 2021-03-04 05:35:40
Rating: Explicit
Warnings: Underage
Chapters: 2
Words: 26,841
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24988414
Author URL: https://archiveofourown.org/users/SewerWitch/pseuds/SewerWitch
Summary: There was that nervous pit in Senku's stomach again, followed by a cold chill that ran up his bare spine. He never put his shirt back on, which made the nervous pit begin to twist in his guts, a nauseating realization hitting in record speed.He had basically just sent a nude to his mentor.
Relationships: Ishigami Senkuu/Xeno
Comments: 28
Kudos: 114





	1. Give and Take

**Author's Note:**

> heyo
> 
> so uh, yeah that new chapter (156) awoken something within me, so here you go. 
> 
> this is not only my first DRST fic but also my first time writing for Senku or Xeno so please be kind if things are a little OOC. I do my best~

* * *

School had become boring. For Senku it was just a day-to-day grind of pretending to listen in on a lecture he already understood, all while getting lost in his own studies that were _grades_ ahead of his own (if not already college level - those were his favorites). Luckily, the teachers had all already learned at this point that there was no point in scolding him. He knew his stuff, still got top grades in the class, and could never be called on during class and give a wrong answer. Sure, his English skills could be sharper, but he was getting more lessons from the internet than his school teachers at that point.

So, school was boring, for the most part. Aside from science clubs which... _also_ let him do his own thing, leagues ahead of the others, only really using it for a space that had some free chemicals and lab equipment. A lab away from home, with shittier hardware, essentially. 

Coming home, though, that always brought a surge of excitement. An excitement that would grow larger the closer he got to home, and nearly explode from him in the act of tossing his school bags onto his bed and nearly throwing himself into his computer chair. Throughout the week, he had been participating in his usual back-and-forth emails with his 'mentor' from the States. A real, bonafide, _actual_ Nasa scientist. 

Today was no different, tapping on his phone throughout the day, sending his mentor an array of questions and theories on the topic they had previously been talking about. Weekdays, that's how it always went. But today was a weekend, or at least it was finally a weekend for them both in their respective time zones. Weekends were a bit special, allowing Senku to bring up a messaging app on his computer. He didn't have too many people on it; his dad (on mute, or else he would be getting nonstop messages all day), Taiju (not on mute, but on some days Senku was tempted), and Dr. X. His mentor. 

It was quite clever of him in the first place - the nonstop quick emails back and forth getting a bit tiring when you had to constantly refresh an inbox. Eventually Senku urged his mentor to just talk to him through the app, which still allowed for file and image sharing, so it all worked out. He half-expected Dr. X to refuse, still entirely unsure if this guy was some brittle old scientist who stuck to the internet basics. But he agreed - with the consensus that such rapid-fire conversations were saved for the weekend, when they could both actually be awake at the same time. 

Senku's hands slid across the keyboard as usual, fast enough that even his computer - as decent as it was - would begin to stall and have to catch up. He had a load of questions on his mind that day, after reading Dr. X's recent email, and he knew this man had the answers. But, it didn't hurt to throw in a few of his own theories into the mix. Whenever his mentor would actually praise his own hypotheses, _that_... that was honestly a big bonus to all of these talks. 

He pressed enter, eyes watching the previous weekends conversations shoot up and away with his new block of text. At first, he would worry these were too much, that taking it down a few notches may get him better results. But Dr. X never shied away from these text walls. 

Senku quickly glanced to the corner of his computer screen. Four in the afternoon - this meant that it would be in the _very_ early morning hours for Dr. X, around one or two in the morning. The late night hours were why Senku could only really expect the instant messages on the weekends, but this was totally fine - it meant he could spend the entire week prior thinking of the perfect things to ask that worked well with an immediate response. 

It came with a sense of importance. His mentor always willing to stay up late, just to talk to him and fill his mind with every bit of knowledge that could fit. Sure, there were probably other things that kept Dr. X up late; his own studies, papers, maybe even just whatever sort of entertainment media the guy liked (Senku never asked - but he wasn't interested in non-science hobbies anyway). But Dr. X's responses were usually quite quick, meaning Senku held a place of priority. A thought that would usually cause a cheeky grin as he typed away at his computer. 

There wasn't a response just yet - that was fine, it all depended on when Dr. X would actually get online. Senku busied himself then, digging through his school bags to find some of the graphs and papers he had started up that day in school. _Getting through the atmosphere,_ that was his current problem, rocket wise. Sure, you can make anything go _up_ if you know how and get the numbers right. But damn if gravity isn't a nuisance. And, with Dr. X's help, he could easily conquer the issue. 

A soft _'blip'_ noise from his speakers signaled a new message in the chat - causing Senku to wheel his computer chair right back over to the screen, eyes excited - but expression falling flat as he saw the very short message that was sent to him. He didn't even need to read the message yet to know that it was way too short to hold the answers to all his questions.

_\--You'll have to give something in return for that._

Senku's first reaction was to just scoff, chin in his hands as he stared at the words. His brow furrowed at the message - this was the first time Dr. X ever suggested something in _return_ for all these lessons. Senku figured it was always some sort of ego boost that fueled Dr. X, to be able to act smart as hell to some kid across the globe. But maybe he was wrong about that, in the end, thinking that this whole thing was going to come at no cost at all. Teachers and professors _are_ supposed to get paid, after all. 

Even with this thinking, Senku's fingers quickly typed out his initial thought, being ' _nice try, I'll just Google it._ ', but he couldn't actually send the message. 

All of Dr. X's lessons, so far, have been ten billion percent more useful and knowledgeable than any google search could ever provide. Not only were they to the point, but were customized for Senku and what he needed to know, which was something that a simple science thesis wouldn't give him. 

Senku erased the message, letting out a sigh. Whatever - it wasn't a big deal in the end, anyway. It wasn't as if Senku was asking where to purchase uranium, or some weird black market chemicals. 

**\--Fine, what do you need?**

_\--Aid in an experiment, of sorts._

Oh. _Wait_ \- this caused a rush of sudden excitement, Senku's fingers lightning on the keyboard once again. 

_\--Like what?_

Senku watched the chat with a large grin, fingers gripped into his palms. They had both talked before about their own experiments and adventures into science and chemistry, but it was always a solo thing, and only talking about the results thereafter. But an actual ongoing experiment? That he could aid in...? Something so far ahead of what his science club would try to make him participate in?

Three animated dots appeared above the chat window, signaling that Dr. X was responding. They stayed for a while, before disappearing. A few seconds later, they would be back, only to leave once more. Senku watched the flighty dots for a few minutes, his excitement turning into an intense on-edge feeling. Usually, his mentor typed a lot like Senku did - fast, never ending, to the point, and immediate. Which could only mean, with the way he was typing now, that there was a lot to this project. Which _also_ only meant Senku felt more antsy in his computer chair. 

He distracted himself, though poorly, with work on his own gadgets around his desk, still glancing constantly at the chat window on his computer. Maybe Dr. X left his computer? Maybe something came up. Either way, the dots were gone now, leaving Senku to ponder on his own what sort of experiment they'd be doing. So, he did his best to distract himself on the 'scientific destruction' of the engine on his desk, but as soon as the soft 'blip' hit his ears, he sailed right back to his keyboard, anticipation bubbling in his stomach. 

Only, to yet again, be met with a single sentence reply. Before reading it, Senku rolled his eyes with a groan. _This better not be Dr. X's new norm, getting him all riled up just to take it all away in a split second._ With another sigh, Senku read the message, eyebrows soon knitting together in a rare feeling: _complete confusion._

_\--A photo of yourself._

That was it, no real explanation. Dozens of experiments ran through his brain, most of them falling on some sort of body-change documentation. Senku was, in no way, willing to do any extreme diets or exercise routines. Though, Taiju would make a good person to experiment on, and would probably be eager to help, anyway. 

The dots were back, Dr. X typing once more. Maybe his mentor was just curious...? They never showed what they looked like in any capacity, just faceless icons in their email profiles or on the messaging app. In complete honesty, Senku never once cared. He envisioned Dr. X to be someone similar to his dad, old and pretty basic. But having a face to the emails wouldn't hurt.

_\--No faces, that's the rule, from here on out._

The new message caused Senku's brows to knit together once more, lips a straight line. Okay, there goes _that_ theory. No face - but a picture of himself. Also, the inclusion of 'faces', being plural, meant his mentor wanted more than one, either now or in the future. But making it a _rule_ was pretty weird. 

Senku typed away, still feeling a hint of uncertainty. There was no point in taking a picture of something when he had no idea what the hell was even wanted. 

**\--Okay? You'll have to give more details than just that.**

As soon as the message was sent, the three dots appeared once more, Dr. X preparing a reply...

* * *

Senku stood in his bathroom, brows furrowed at the iPad held in his hands. There was a pit in his stomach, either something telling him that something was off, or that he was simply hungry. But trusting his gut was never really in the cards for Senku, in fact it was quite the rare gesture. Instead, it was easier to focus on the facts at hand, and the facts at hand were a simple message staring back at him. 

_\--Torso, no shirt._

Short and sweet... though, calling it _sweet_ was a bit of a stretch. There was still no explanation at all, but it was easy to guess what his mentor wanted from this...

Body mapping!

Simple enough. As he thought, this was most likely tracking a change somewhere. Even so, Senku felt his eyebrow twitch just staring at the message, that sick feeling refusing to leave him. Dr. X's messages were never this short, or simple. 

Maybe calling up Taiju was actually the best bet, here. If Dr. X was going to make him start some crazy weight lifting regimen just to document the changes in muscle growth, well, Senku just wasn't the best person for that at all. 

His fingers slid across the iPad screen, swiping through apps until he found the camera, flicking it on. Senku wasn't above doing a few experiments on himself, as long as they weren't a life balancing act...

Senku pulled his shirt over his head, ignoring again how weird this felt. With his arms held high, iPad covering his face, Senku took a shot of the bathroom mirror. The resulting photo was... well, totally useless. The lighting was horrible, let alone the flash had reflected on the mirror, though that was just a rookie mistake. Selfies were... _not_ Senku's forte. At all. And this picture wouldn't aid his mentor one bit. 

With a sigh, Senku quickly changed up his makeshift studio, dragging in a lamp from another room as well as opening the bathroom window for that added _natural_ light. With the flash turned _off,_ Senku raised his arms high again and snapped another photo. 

It was... better, he supposed. Senku wasn't narcissistic enough to really care much about his body and if it looked nice, but that was far from the point. He'd have to properly crop out his face, but was the best he could do, and just for added measure he could add a footnote to the message saying that his best friend was a much better guinea pig for body-focused experiments. 

Senku made his way back to his room, giving a few simple swipes and taps to the iPad to edit and send off the image. Back at his desk, Senku placed the iPad down, able to switch over to the computer. Luckily, his picture didn't stare at him in the face, which would have just felt embarrassing. But, it did show that an attachment had been sent, and the small green icon next to Dr. X's username showed that he was currently online, so he had probably seen it already. 

Which... honestly just felt weird. There was that nervous pit in Senku's stomach again, followed by a cold chill that ran up his bare spine. He never put his shirt back on, which made the nervous pit begin to twist in his guts, a nauseating realization hitting in record speed. 

_He had basically just sent a nude to his mentor._

A laugh fell from him, nervous but shaking off his doubts. There was no actual way that was what this was about - this was purely for science! Pretty soon Dr. X would be giving him proper details on what exactly they would be doing with this. 

But no reply came - only a check-mark next to the image confirming that it had indeed been seen by Dr. X. That didn't help the nervous pit leave at all, only letting it churn, causing Senku to message first. 

**\--Well?**

Message seen - but no typing from Dr. X at all. Senku began to type again, speed rising with his apprehension. 

**\--Look, if you want I can get my friend to come over, he really is a huge meathead, he'd be perfect.**

_\--No, there is no need._

Senku's hands paused, fingers curling into his palms, feeling his nails dig a bit against his skin. 

_\--It's absolutely perfect, thank you._

A... compliment? Senku's cheeks felt hot, his brows knitting close together, hurriedly scrolling back up to click on the image attachment. It wasn't weird, right? Well, _yes,_ okay it's a little weird, seeing his half naked body in his own bathroom (with some pretty well done lighting, if he could say so himself), but his face was cut out... that was the important part, right?

Okay, no, on second and much more fuller thought, this was over ten billion percent weird. 

He needed to combat the weird, typing again at his mentor with a feverish speed, needing answers. Proper ones. 

**\--Okay, what is this for, though? Because I'm not doing any weird diets or exercise routines, even IF you answer all my science questions.**

Luckily, like before, his message was met with Dr. X immediately typing up a response. 

_\--You'll hear more about it very soon, thank you again for your cooperation._

"Maaa~n, what the hell," even with no one in the room, Senku couldn't help but say his frustrations out loud, relieving an itch in his ear as he did so. This entire conversation was nothing but annoying, in the end. _Whatever,_ a change in topic wasn't a bad idea, and it'd allow him to forget about maybe, possibly, but not _really_ sending a nude to his mentor. 

Maybe Dr. X really was like his dad, in the end, annoying as hell. He just hid it a lot better. 

* * *

Senku was, for once, on his bed that afternoon. Summer was getting overbearing at that point, and the air conditioning unit sat above his bed. That wasn't to say he was wasting his time, instead just lost on his phone, scrolling through his usual internet haunts. Though, that afternoon, as much as the theory of quantum physics could excite him on a normal day, his mind kept drifting. Eventually, he would be getting an email, or a message. Possibly both. 

The email alert eventually came through, both through his phone and a noise popping from his computer. Senku glanced that way, eyeing his computer screen lighting up with the sudden activity. He could move there - it was easier to type on a keyboard after all. But it was the weekend. _Weekends have changed._

Weekdays had mostly stayed the same as always. Long, detailed emails between the two of them, back and forth, about the topic at hand. It would go on until Dr. X would change subjects onto whatever he felt was best at that time, something Senku didn't entirely mind. Sure, a lot of this was still for his rocket (he had managed to build another once since meeting Dr. X, but it blew up way before reaching the earth's atmosphere), but learning every corner of science, that had a nice ring to it, too. 

Weekends, though. Like before, weekends usually consisted of their chats migrating to more instantaneous messaging systems. It proved to let them chat a lot faster, but the means of instant messaging also caused conversations to grow a lot more casual. Sure, they still talked about science and their current projects, but those conversations always changed. Some days, the change was gradual... others, sudden. Senku still couldn't figure out if there was a pattern to it, figuring it really was just up to his mentor's mood that day. 

He brought up the email on his phone, knowing that there was no actual point venturing to his computer, not that afternoon at least. Instead, he stood up to walk to his window, scrolling through his inbox as he ensured the blinds were fully shut. It was the usual detailed response that Dr. X would give him, this time even including links to store pages and online reports. This guy had en ego - Senku had definitely learned that much. 

Another message popped up on his phone, this time through the messaging app. The preview only read one word. 

_\--Senku._

His bed squeaked as he fell back onto it, clicking into the app, and typing out his response with a single thumb. The conversation was simple - a quick back and forth, his mentor asking how his current experiment was going, chiming in with a tip or two (or a dozen). This is always how it started. 

He was a total idiot for not noticing it sooner. 

No, no that wasn't quite right. Senku had that gut feeling the first time he sent that picture over, but it was easy to ignore and force logical reasoning onto it. 

He could have stopped all communication when the other requests came through, though. More skin - little by little. Sometimes it was something stupid, like a kneecap, an ankle. Easy to disregard, but also so obvious at the same time. Senku took pride in being able to easily read motives, but Dr. X was a strange one. His requests weren't comparable to the standard type of 'send nudes' you'd see across internet compilations or memes. At least, not to Senku. They had his usual style of elegance to them, even if short and to the point. 

He knew the whole time, deep down, what this was. He could have backed out at any given time when the requests became more risque, demanding more vulnerability on his part, showing a lot more than just _skin._ But he didn't, instead playing along, giving his mentor exactly what he wanted. Naturally, the promise of more knowledge was a huge reason. If he kept his mentor happy with something as simple as a picture, he could keep this guy around for as long as he wanted. But there was something else, an emotion that didn't always pop up, one that gave off enough dopamine and serotonin to actually cause Senku to feel off balance. An emotion he usually tried to ignore, but damn did it love popping up when these messages would start...

A few pictures were sent back to him, over time. Only a few. Dr. X was not as keen at sharing photos of himself as he was with his knowledge. But damn, if those pictures didn't help seal in that these conversations weren't just scientific in nature. This guy was NOT some whittled old scientist, and _nothing_ like his own old man at all. Young adult - early twenties probably, though it was hard to really tell without a face shot. Even if he worked at Nasa, he must have gotten in during his teens or at least before hitting twenty. His body was... well it was nice, though Dr. X was much less accustomed to sending as much skin as he demanded from Senku. 

An occasional torso, usually still with a shirt (unbuttoned at most). Definitely not a dad-bod at all, lean, though not too built. Senku could tell that he was tall, but it was hard to think of exact measurements when all he ever got was small crops of a body. Even so, they became rare treats, and only _once_ had his mentor actually sent him something that caused a need to hurriedly hide his phone from his eyes in a bout of shame and embarrassment. It shouldn't have been a huge deal - Senku had seen countless dicks on the internet (he's a teen himself, after all, and it's best to get rid of such urges quickly in order to get back to more important things). But, knowing who it belonged to, seeing his mentor's slender fingers wrapped around it, full mast and _excited,_ all because of talking to _him,_ and his own little pictures. 

That's usually when that pesky, giddy emotion set in. That stupid sense of pride, all at making Dr. X riled up because of _him._

A picture of _that_ much importance only came through once. Senku commonly saved most all of the images his mentor sent him, usually because they had to do with their current topics. Graphs, formulas, equations, diagrams. That picture, though, deserved its very own... _very_ deep and hidden folder.

Senku gave a quick glance to the top of his phone's screen, reading the time. As per routine, it was the middle of the night for Dr. X, but a hot afternoon for Senku. His air conditioning may have been on, but his room wasn't chilly enough to warrant staying clothed, at least not when he knew where this conversation would likely be going. He sat his phone onto his bed, screen facing him so that he could still read any incoming messages, and proceeded to unbutton his shirt. Taiju wouldn't be over today, Senku had gotten pretty wise to that. Too many secret conversations in the bathroom while his poor friend waited clueless outside for him to finish. Luckily for them both, Taiju was too oblivious to ever ask why Senku left the bathroom more tired than he went in, or why his cheeks were usually tinted red. 

The shirt landed on the floor with a toss, near his door where Senku could grab it later for laundry pick up. His phone continued to vibrate with new messages, but Senku found himself waiting for something else. Occasionally, there was a weekend that they didn't follow this routine. Things would come up, work would be too grueling, or perhaps his mentor was just not in the mood or too busy to start things. And Senku, well, Senku wasn't the type to beg. 

So he waited, it was only a matter of time. Dr. X was pretty active at the moment, still sending messages on his own accord, even without Senku replying just yet. He didn't have the gull to break up the chain of conversation, letting his mentor continue his chatter of processes and theorems. Senku laid back then, watching the chat window fly up constantly as new messages rolled in. It was fine - he enjoyed reading them all the same, and the anticipation was a bonus. 

There was a chance, yes, that this would be a weekend without any... 'extracurricular activities', but the odds seemed to be in his favor tonight, with how active his mentor was. Eventually, a command would come, and it would spark an entirely different sort of conversation. 

Senku never actually imagined he'd be the type to like commands. In all honesty, he never really felt that anyone had a pure authority over him, aside from actual law enforcement (who had sent him home from the park a few dozen times, forbidding him from conducting experiments. Then again, that only meant he needed to be sneakier, or find new places). Even his teachers couldn't really tell him what to do, eventually giving in and letting him do as he pleases. And his dad, well... honestly his dad was the easiest person to deal with. 

This, though. It was different. Dr. X had a completely different _feel_ about him, he could tell that even over the internet, thousands of miles away.

Senku _also_ never really thought about sexuality. Girls were fine. Guys were fine. Everyone was pretty much fine, but only really _fine._ A certain face may strike him as particularly nice to look at, and a well sculpted physique was always something he could stare at (and study) for a while. But this faceless man from across the glove, currently breaking down mutations and human genomes through a phone app, was doing all of this unnecessary work just for _him._ Even if he was showing off by doing so, his mentor was putting everything down to fill his own brain, just to teach him. 

Senku, however, was _also_ not one for poetic flare. There's little to no logic behind romantic urges aside from getting a fix of 'happy chemicals', as addicting as those are. Not to say that there's anything wrong with it, feeling happy is an important human necessity. But it was hard to think straight with emotions like that. Even less so with sexual ones. There was no real point in thinking hard about it. This relationship was simple. Give and take, and luckily the _giving_ part was beneficial to Senku as well. 

Senku reached downward, eyes still focused on his mentor happily chattering along. It didn't take much effort to undo the belt and buttons there, making the ease of access a lot more open. Dr. X made him excited - it was as simple as that. Made him want to please. Be praised. The latter not happening too often, but when it _did..._

A sigh left Senku's lips, his eyes closing as his hand began to slide beneath his briefs. It was easy to get lost in it, the hand that held his phone soon resting against his forehead, his grip softly changing each time a new vibration from his phone would ring against his skin. Vibrations that eventually stopped, in turn causing Senku's palm to cease it's movement as well. He brought his phone down to see the messages, the final one simply being his name. Dr. X must have noticed his absence. 

Senku quickly began to type up an apology. 

**\--Sorry, distracted.**

_\--Senku._

_\--Are you already hard?_

It caused him to gulp, a quick laugh escaping his chest. It wasn't as if he was trying to fool the guy, nor was he forbidden to touch himself. Even so, his mentor caught on, and Senku didn't even say a thing (quite literally). 

**\--Oh yeah. Whenever you bring up the human genome, that's when things get really hot**

_\--Senku._

His wrist ran across his brow, wiping off the bits of sweat that already began to form there. Dr. X wasn't too keen on his snarky jokes, which made using them even more fun. 

_\--It's quite unkind of you to not show your work._

There it was - not quite a demand or request, but just enough. Anticipation was growing in his stomach again, that bubbly feeling that always came with these conversations, one that always sent a wave of warmth to his groin. Damn, it was so easy for this guy, wasn't it.

Of course, Senku couldn't just give his mentor _exactly_ what he wanted. That would be giving in way too easily. 

It didn't take too much readjusting of his clothing to make things look perfect, Senku soon holding his phone high to get a downward picture of his torso and hips - pants still on, but barely showing the hem of his briefs. It was obvious there was a bulge there, just enough to tease with. 

**\--Show you what?**

He followed it with the picture, doing a usual quick glance to make sure nothing identity-leaking was in the shot. As soon as it was sent, he began to set up the next one, knowing this wouldn't please Dr. X one bit. No pants for this one - tossed to the floor alongside his shirt, but his hand gripping and covering the erection between his legs. Of course, it couldn't be done without taking a few moments to grind his palm against the fabric, sighing again. The picture showed mostly his legs and hand - no real bulge this time, only the knowledge of one hiding. 

_\--You know exactly what I want, Senku._

The second picture went through now, followed by Senku's own response.

**\--You sure have a weird way of NOT saying it.**

Senku fully set up then, placing his back against the cool wall beside his bed. He watched as the dots showed beneath the chat window, Dr. X sure to totally (not) be happy with the image. 

_\--Are you enjoying your little game?_

It caused Senku to snicker, choosing to not respond just yet. There were times that these conversations never included a single photo - sometimes it was simply a demand. But occasionally, Senku got a reaction. That was the best part. 

His hand slid beneath his briefs once more, this time fully taking his cock out, eyes closing as let his hand slowly begin a weak pace. Nothing too rushed just yet - there was no hurry here. 

Dr. X had not sent another message yet. This was fine, and honestly expected. Senku had never once actually got his mentor to beg for anything. It was a nice goal, certainly, but one that Senku didn't lose any sleep over. Even so, that didn't mean it wasn't still fun to try and entice more pronounced demands from the man. 

**\--How about a video?**

_\--No._

Dr. X's response was immediate, which at least meant that he was still being quite attentive to the chat. Videos were _always_ a no-go. Too easily exploitable, but damn it was still fun to tease. 

**\--Are you sure? The lighting in here is great. Summer afternoon, and all.**

No response came, the silence becoming a great reward for Senku. Was he annoying his mentor? In a way, that sounded amazing. Senku had no idea what the man looked like, but the idea of causing a grimace or two on the older man's face was enticing enough in itself. If he could actually muster up some decent dirty talk, Senku could maybe feel like he's won something against his mentor, but dirty talk wasn't exactly a specialty of his.

Senku's phone vibrated with another message, the boy's proud smirk suddenly twisting as he viewed the words on his screen. 

_\--How about a phone call, instead?_

Every bit of motion in Senku's body paused, both hands coming up to hold his phone as he sat up onto his knees. His brows furrowed together, body feeling both way too hot and way too cold in that room. 

**\--What?**

It was all he could really muster up to type. 

_\--According to prior conversations, your father isn't living at home right now. Is there anyone else living there?_

**\--No.**

It prompted Senku to wildly look around his room, as if someone would be outside his window just then. But no, his window was shut, curtains closed, his front door locked - Taiju had a key but Senku had also made sure to tell Taiju to not randomly show up due to 'needing quiet time to work on things' that day.

Does he... actually want to call...? Wait --

**\--English, right?**

Everything had been in English at that point, at least from Dr. X. Hell, a huge reason Senku's English was getting a lot better was because of these constant conversations, and a bit of help here and there from Dr. X when Senku couldn't find the proper translation for bigger more complex words and phrases. He felt decent enough in it at school, acing any test and being able to read aloud just fine, but actually talking _out loud_ to his mentor, someone with the language being their native language... 

_\--I would humor you, but your English is a lot better than my Japanese, at least right now._

Was that... a compliment? It was a little disguised, but it sure as hell felt like one, and it hit Senku's chest just the same. A swell of pride rose in him, enough to actually--

Wait, _wait,_ was this actually happening?! This wasn't even a call to just discuss some medical terms or mechanics of rockets, this was... _purely_ for something entirely, _ten billion percent different...!!_

Senku gulped down his nerves, knowing full well there was no actual reason to panic. If things got weird, he could hang up, and refuse to ever do this again (probably).

 **\--Fine, call then.**

As soon as the message had been sent, anxiety began to churn in his stomach. Which was entirely stupid - phone calls weren't a huge deal at all, but the gross feeling in his gut wasn't leaving. How should he even answer the phone? How do Americans usually say hello? Maybe Dr. X would say the first words, and then everything after that would be fine, just a normal... conversation with his science mentor from across the ocean... on his bed, with his dick out, after sending suggestively erotic photos. 

Senku began to rub his face, cheeks warm, groaning softly at the idea of it all. Why the hell did he agree to this?!

The sudden and more erratic vibrating of his phone threw his thoughts away, though it didn't throw away his apprehension. It was the same app they always used, but now the bright digital letters spelled out 'voice call' with Dr. X's username above it. There was no going back after this. 

With a quick swipe, Senku answered the call, bringing the phone to his ear - his other hand moving to his other ear to quickly itch at it, a habit that had been forming. 

" _Man,_ you're that desperate to hear my voice, old man?" Yes, start it off with snark. That'd solve everything. 

"Senku."

It was just his name - as usual, always, just his name being said to gain his attention. The man's voice was deep, but sharp, able to make Senku stop all his actions and listen. 

"Yeah," he had to respond with something, to let Dr. X know that he was there, but all other English words were leaving his vocabulary. 

"You're quite the brat, aren't you?" the voice said then, causing Senku to choke out a nervous laugh. 

Senku only hoped the laugh didn't _actually_ sound nervous. The last thing he needed was his mentor knowing that he was totally out of his element right now. But even so, he had no idea what to _fucking say...!_ Science was way easier, if they were at least talking about anything else he could come up with the words, but just spouting off some nonsense right now would make it totally unmistakable that he was super on edge!

"Senku," oh, thank god, Dr. X was the one speaking instead. Senku's shoulders slumped, sitting back again with his back against the wall, "tell me what you see right now."

" _Eh-?_ " The noise was compulsion, but Senku took another glance around his room. Sort of a... strange request. He could just take pictures of his room if the guy wanted to look around. "My room...? You want me to tell you my decor? Weird, but okay."

A chuckle came from the phone, a noise that shot a new warmth into Senku's body. 

"Sure, that's fine," his mentor mused, his tone seeming to imply that this was not at all what he meant, but the results were still satisfactory for him. Senku's snark bit him in the ass, on that one. 

"Right, uh," it was just a room, in the end. Senku talked about his stations, his computer, only a few times having to pause and think hard about the proper English words for some of the bits of equipment scattered around. Eventually, he ran out of obvious things to talk about, soon coming back to himself, "and, my bed, where I'm sitting."

"Ah - so you're not at your computer?" Dr. X began, pausing for a moment and seeming to be typing, a few quick tacks to a keyboard being heard. "I figured you would be there." 

"What?!" Another immediate response from Senku, "no way, I don't usually--"

Shit. He paused, hands gripping. That was close - though the fact that he stumbled over his words was frustrating. He wasn't too flustered to say these things through text, so why the hell is this so different. 

"Hmm?" His mentor hummed it out, enjoying this. Of course he was. "What is it that you don't do at your computer, Senku?"

He couldn't help but stall, the silence caused by his own embarrassment becoming annoying, and annoyance pushing him to just say it and get it over with. "I don't like jerking off where I do my work. I'd rather not cause messes." 

Senku heard a snicker from the phone. Did he find it funny...? Honestly it was a good call, his stuff was _expensive,_ and buying multiples of one thing was going to begin to look weird on his dad's credit card. Weirder than usual, at least. 

A grumble left Senku's lips, knowing full well that this man was teasing him. "What, so you do it at yours?" 

This time, it was Dr. X who paused conversation, a sense of delight in his tone when he finally spoke, "Senku... Did you really think that during all of these meetings of ours, I've been touching myself alongside you?" 

A cold chill ran up Senku's spine, his grip on his phone turning hard. There was nothing but enjoyment and entertainment in his mentor's tone, something he could hear even despite the language barrier. 

"Uhh," it was hard to find the right words again, put on the spot, "what else would you be doing?" His mind shot back to the pictures he had received. The few of a body, yes, but there was at least one that was still perfectly ingrained into his mind, the one saved deep in his hidden folders. Maybe it _wasn't_ his mentor this whole time?! Senku never thought twice to do a reverse image search, but... Dr. X wasn't that shady, there was no way...!

There was another chuckle from his mentor's end, "from time to time, I can't help myself. You can become quite convincing, Senku. But... for the most part," Senku could hear a bit of shuffling as the older man paused, moving around on his own side of the call, "I find it... _amusing._ " 

Senku's brows began to knit together, unsure how to respond. Was this... just a game? Well, of course in a way it was just a reason to jerk off and connect a bit to someone he looked up to...? Shit, maybe even _that_ was looking way too much into it. 

"You never finished telling me what you can see."

"Eh?" Senku's mind was luckily ripped away from thinking too deep on the subject, at least for now. "There's nothing else, I told you everything."

"Yourself, Senku." 

"Oh." Oh. 

Senku could feel his cheeks getting hot again, reaching up to rub at them. _That's_ what they were doing. Right. A sudden bout of discouragement hit him - _damn_ he was bad at this. At least he could stay up to par when dealing with this guy and these things through text...! 

There was no point in delaying, it would only make this feel more awkward. "My, uh. My shirt is gone," he glanced at his small pile of clothing near the door. He had forgotten to mention those. 

"And when did you do that?" 

"Earlier, the air conditioning isn't on," a bold faced lie, but there was no way Dr. X could tell. "it's pretty hot in here." 

"Ah, so after we had begun talking?" 

"Yeah..." that much was obvious! There was no point in asking that - it wasn't like he took his shirt off as soon as he got home, and he _knew_ they'd most likely begin going down a route like this. 

"And? Is that really all? If we bring up your most recent photo," there was a pause from Dr. X, the idea of him digging up past photos of Senku causing the boy to grow more flushed, "it seems your pants are already gone as well. Quite the detail to skip over, Senku." 

A scoff was Senku's first response, a quick defense. "Yeah? So they are." He knew exactly what this guy wanted. More details. His dick was still out, a lot less eager now that his mind had become so preoccupied, but it still sat there. It shouldn't be that hard to say. Just _say_ it, tell him that your dick is out, that it's needy and wanting to be touched and--

"Is your cock out, Senku?" 

A relieved sigh escaped his body, shoulders slumping as tension left them. He asked first, that makes this a lot easier. "Yeah," he said, voice low. If Dr. X continued to guide this conversation, maybe something would actually become of it. 

"Good, grab it for me." 

A proper demand - no guesswork to be done, making Senku's hand move automatically. He wrapped his palm around himself, softly for now, only giving small pumping. He had lost most of his hard-on before, but it was quickly coming back to life. 

"I'll be curious to see if you make these sorts of noises the entire time, Senku." 

Damn. Was he making noises? It was entirely possible, in fact he must have if it was enough to entice a reaction from Dr. X. Senku gave a small scoff in return, defenses still feeling a little too high, "what, it's natural." 

Dr. X then gave a small hum, "Senku, put me on speaker. I want you to lay down, you can put your phone anywhere but I don't want it too far away from your mouth." 

With only a bit of hesitation, Senku pulled his phone away from his ear, taking a moment to stare at the screen. Minutes slowly counted down their call time - it hadn't even been that long yet. The speaker phone button was tapped, the color of the call window changing. More static could be heard through the speakers now, and Senku laid the phone next to his pillow, soon placing his head there as well. 

"Did you let go?" 

Hearing his mentor's voice through the speaker phone was... entirely different. Sure, the tone and pitch were a little more distorted, but he felt _closer_ somehow.

"No..." Senku's hand pressed his cock against his belly now, the tip just beginning to leak a small bit of pre. Technically, it was not letting go. 

"Very good. You do realize what we are going to do, correct?" Dr. X questioned, an inquiry that Senku had no real answer to. But it was no matter, his mentor continued, "I'll be telling you exactly what to do, how to do it, and how long to continue. And you will comply. Understand?" 

"Yeah, yeah," Senku had the compulsion to begin nodding - but stopped himself, knowing the person on the phone couldn't see him, "it's not so different." It wasn't, not _really._ Though, usually it would come in quick demands, certain photos, or proof somehow that he was doing exactly what he had been asked. The immediate gratification of an instant message was nothing in comparison to this... 

"Perfect, then. I want you..." a small pause, perhaps he was thinking? "go ahead and stroke yourself, softly. Keep your grip light." 

"You _do_ realize I know how to jerk off, right?" 

"Hush," it was sudden, and even though his mentor's tone was soft, Senku couldn't shake the feeling of being scolded. "Close your eyes, as well." 

A sigh left Senku, but he complied, readjusting himself on his pillow and finding a comfortable position to continue in. Soft strokes, teasing, that was the whole point here. The gentle grip was not really causing much pleasure at all, but his dick still grew harder in his grasp. It still felt nice, as one would expect, like any sort of masturbation session would feel. But the static white noise of the phone next to him only made Senku more aware of everything going on. His breathing, the shuffling of his shoulders and hips, his _noises. Did_ he make noises?! He never actually paid attention to that before... 

"Your free hand," Dr. X's voice cut through the silence, "run it up your torso - gently now. Barely enough to register touch."

Senku listened obediently without responding, his other hand now running slowly up his body, the tips of his fingers just barely ghosting against his skin. The slight tickle of it all, nerves firing awake, was enough to cause his breath to hitch in his throat. 

"Once you've reached a nipple, I want you to tease it - I'm sure you don't need me to tell you how." 

Another defensive scoff left Senku's throat, but he listened all the same, his hand finding his way to one of his nipples. It was... embarrassing, to say the least. Senku hated to consider something like nipple play a _weakness,_ but the soft teasing and flicking of the sensitive mound always left him feeling a certain sense of vulnerability. 

"Your grip, is it still soft?" 

"Yeah...?" 

"Do you want to go faster? Grip harder?" 

Shit. Senku grit his teeth, hips starting to shift more against his touch. Yeah, he wanted to, but this guy was trying to make him _beg_ for it. He took a deep breath, going back to his usual snark, "Well _yeah,_ it would be nice, this isn't doing much." 

His mentor gave another short chuckle, "Then do so." 

Senku let out a loud huff, feeling annoyed, though unsure if it was at his mentor or at the fact that he was enjoying this. His grip changed, tighter now, which of course felt _great,_ but...

"What are you doing...?" Senku couldn't get the question out of his head, so he may as well throw it out there. 

"Hmm?" Dr. X only hummed in reply - a little odd to pick up, the inflection at the end letting Senku know it was a question in return. Language barriers are still a bit to handle. 

"I mean, is this..." his hand movement on his cock ceased for a moment, making sure his words were right, eyebrows furrowing in thought, "are you just doing this for your amusement again?"

Senku only got another hum in return, causing the boy to give a deeper sigh. Whatever, he could live with that, in a way it meant he was putting on a show, which was enough reason to continue. His strokes started up again, eyes closed as he allowed himself to become lost to it, wondering if--

A vibration sounded off from his phone. Logic told him that it was most likely a message from Taiju (or worse - his dad, not something he wanted to see right now), but curiosity still caused him to glance over to the call. 

Dr. X. 

Image received. 

He had sent a picture over. Senku's stomach began to twist, in a good or bad way he wasn't too sure yet. His hand shot out, grabbing the phone, swiping through windows to get back to the messaging screen. 

"Ah - You cannot stop, Senku," shit, he must have made too much noise moving around. "Even if you're on your phone, I want your grip tight. Keep stroking, all right?" 

Senku began to chew on his lip, only able to hum back in response. He listened, to the best of his ability, hand stroking his cock with a new surge of excitement as he clicked through and opened the image. 

He couldn't comply then - his moving stopped entirely, but his grip turned tight. 

It was the usual point-of-view shot that he would send his mentor all the time, but damn was it already rare to get one in return. Dark pants contrasted well against the main focal point - his mentors cock, hard and held in that elegant careful grasp once again. In the background it was easy to see a desk with a distant computer, a myriad of papers and folders, and a single coffee mug. 

"Seems this is one of the times I cannot help myself," his voice dripped with amusement once again, clearly enjoying this. 

Senku couldn't look away, eyes focusing on the computer screen in the distance. It was poor resolution, but he could just barely make out the same diagrams that Dr. X had sent him just a while ago. For sure, this was a genuine picture. 

"Perhaps it's the noises you've been making. Coming from such a bratty kid such as yourself."

Senku gave another quick huff, letting his phone fall back onto the bed beside him. "So... what is this?"

"Hmm? Is it not obvious to you?" 

"No! I mean--" Damn it. If he had his damn dictionary up, thinking of the proper words wouldn't be this damn hard. 

Luckily, Dr. X seemed to catch on, answering for him, "everything I tell you to do, I will do as well. Call it a shared pleasure. But there is a rule, Senku." Senku could hear his mentor shuffling, the thoughts of him stroking his own cock at the same time sending a wave of warmth down his body. "You must not come before I tell you to. Understood?" 

"Yeah, yeah..." Senku's eyes closed once again, finding himself back in a comfortable position. 

It wasn't as if it was anything out of the ordinary. A command to change his pace, pumping speed becoming faster - the eventual command to bring his other hand down to cup at his sack, his palm teasing and massaging the tender spot in rhythm with his hand. There could have been more of a _slickness_ to his grip, the bits of pre leaking not exactly enough to make it a smooth ride, but there was no way in hell Senku was going to give his mentor the satisfaction of hearing him spit into his hand. 

Dr. X was sitting at his desk, Senku knew that much. With his eyes closed, it was easy enough to imagine, even if Senku had no face to picture. He could at least imagine that delicate looking hand, sliding across his mentor's cock at the same pace and rhythm as his own. Was he in his home office? Or was he at work? No - no, Dr. X was probably not _that_ daring... 

But even then, still just following along - if he listened carefully enough, perhaps Dr. X was making noises as well. Senku couldn't fully focus on that, though, only able to engross himself in the images in his head. Was his mentor laying back in his chair? Maybe his feet were propped up? Were his eyes also closed, or was he doing nothing at all and just listening to Senku's noises. 

He was much more aware of them at that point - the small moans and shudders that left him. Nothing too erotic, not to him, but the idea of them sounding nice across the phone line, that was enough. There was a definite peak rising, a tightening in his muscles that signaled it was soon, the urgency of it causing his pace to quicken. 

"Senku. Stop, now." 

He did, panting softly. A few deep breaths, just to keep his body from plummeting over the edge of a wasted orgasm. It was a good call - too soon, and besides, wasn't there a demand to not finish until told...? A bit harder to fake it, on an actual call, if he messed that up. As soon as his imminent orgasm had calmed, Senku heard the voice of his mentor once again, allowing him to continue. His grip was tentative, careful, not wanting to race back to the cliff too quickly. 

It became a pattern then - commands meant to just tease him and force him to get dangerously close before stopping again. Technically, truthfully, nothing was really making him stop. Dr. X couldn't actually _see_ him, if he was quiet enough he could probably come and not give it away, right? Maybe it was wishful thinking, but every time he was told to, Senku still stopped, soon pulling his hands to rest above his head with a loud groan. 

"It's quite easy to tell, Senku," there was a chuckle - but now without the noise and commotion of his own movements, Senku was able to make out the slightest hint of his mentor being out of breath, "even just from your noises, when you're about to finish." 

Senku only answered with a quick scoff, happy in that moment that his mentor could not see how red in the face he must have been. 

"Do you want to come?" 

Another scoff, this time looking away from the phone as if it was an actual in-body person speaking to him. Dr. X was trying to get him to beg - and it wasn't going to happen. Not as long as Senku still had even a small sense of control. 

"Hmm, well. All right. I'll need you to turn over for me, Senku." 

Senku gave a hard blink, but quickly began to twist his body, but soon stopped once he was on his side, glaring at the phone, "Wait, _you_ can't do that in a computer chair." 

"Yes, our forms may be different, but I still will follow along." 

His eyes narrowed at the phone screen. Dr. X seemed pretty calm and collected, especially if he was just doing everything that Senku was up to just moments ago. He mumbled out a small curse, in Japanese, one his mentor probably didn't know but just the inflections in his voice was probably enough. The position wasn't exactly comfortable, not with his dick still hard and pressing against his bed sheets. 

"Once you've done so, I need you to raise your hips high. On your knees, now, but keep your head on your pillow." 

It was a simple enough command, but as soon as Senku began to comply, a realization hit hard - this position was... really, _really_ suggestive. His face felt warm against his pillow, hell his _entire_ body felt hot. 

"I'll need your knees far apart as well. Have you done so?" 

"Mm," the reply was muffled in his pillow, but it wasn't as if Senku knew a proper response to say, anyway. 

"Very good. Take a picture for me, Senku." 

"-Eh?!" It caused the boy to rise to his elbows, staring down at the phone. This was... _not_ an easy pose to try to get a picture of. But, odds were, this was for proof that he was listening and not a plea for actual good photography skills. With a sigh, Senku grabbed at his phone, swiping quickly through apps until his camera popped up, trying hard to get a good photo through his front-facing camera. He mostly had to trust his gut, unable to see the screen at all, soon hearing the photo-app give a shutter sound.

Looking at the picture... Yeah, _yeah_ this pose was pretty provocative. Luckily his face didn't show at all, only his shoulders down, allowing him to quickly send the photo and drop his phone back onto the sheets. He waited silently, arms wrapping around his pillow to provide a bit more comfort and support. 

Eventually, a soft hum could be heard from his phone. It sounded... happy? _Shit._ It wasn't a great photo by any means but it still seemed to give some sort of pleasure to his mentor. The thought alone was enough to make his dick twitch. _Embarrassing._

"Did you move?" 

"No..." 

"Good boy," oh, that was... for some reason, nice to hear. Dr. X had never used phrases like that before. "Reach down for me, begin pumping again, start nice and slow..." 

The pace quickened soon, just like before, commands urging Senku to change his speed or movements, but this time around the pose added an extra element to it all. Senku had never jerked off in a position like this before. The thought never even crossed his mind. It was almost too much, his body so fully on display - he was thankful that, through all of this, Dr. X never told him to remove his underwear, letting him at least keep that bit of shame to himself. 

Maybe his head being lower than everything else was causing blood to rush to his head, or maybe it was his attempts at muffling his noises through his pillow that was causing a lack of oxygen. But those theories didn't matter, not really. It felt good, and knowing that Dr. X was practically right beside him... 

"When your eyes are closed, Senku..." 

He did have them closed, actually, but opened them to glance over at the phone screen. 

"Who is it... that you imagine? Or what, even?" his voice seemed a bit strained, which only caused more jolts of electricity to flow through Senku's body. His mentor was feeling good, too, because of all of this. "Do you have someone... at your school that you imagine? Their hands, maybe even their month, on your little dick?" 

Senku's stare at the phone narrowed with a glare. His size was totally normal, perfectly average, there was no need for that. But that didn't stop his body from tensing, or his dick twitching at the sensation of being teased. 

"Or...? Do you imagine it's me?"

Senku's eyes shot closed, eyebrows knitted, cursing low again. 

"Do you think of me, each time you get off? Tell me... Senku, who are you imagining right now?" 

"I-idiot-" words were becoming hard, especially when not trying to moan them out, "It's just me," there was no room in his head for fantasies or anyone else right now, only this asshole's voice and the building orgasm. 

"Hmm, then I want you to imagine I'm there, Senku... My hand wrapped around you, listening to your little noises, your body language... just so that I can stop you before you finish." 

As if on a humiliating cue, a shaky moan left Senku, the images of it flashing in his mind. For a second it was possible to imagine that his hand was not actually his own, that it was being controlled by someone else, but logic quickly stepped right back in, "I don't... even know your face, dumbass..." 

"That's not really needed, is it? Not if I'm behind you." 

Senku gave another unwilling and breathy moan, burying his face into the pillow entirely. That's all it really took, the quick vision of a person - not just any person but Dr. X, behind him. Taller, older, much more status and therefore more superior and powerful, holding his hips steady, hand clasped tight around his dick...!

More shaking and desperate moans fell from Senku's throat, teeth clenched tight onto his pillow, the waves of a very much needed orgasm crashing hard. It was enough to cause his knees to shake beneath him, tremors hitting them as his muscles relentlessly spasm. 

A pleased chuckle came from the phone, barely audible to Senku as he attempted to calm his breathing, the sweat across his body making his overheating body feel cold. 

"Oh, was that enough for you? Really? And after I forbade you from coming without being told." 

Senku gave a low groan, body falling limp against his bed, doing his best to ignore the wetness in his sheets. "Shut up," his voice felt ethereal - not his own, "this was new territory!" 

"Ah... that's good to know. I've been thinking of a few new things..." 

Senku's energy bursted back quickly, grabbing the phone with a loud groan as he sat up to sit on his knees, pinky satisfying an itch in his ear, "You already won, don't milk it, it looks bad on old men." He sighed then, looking down to where he was laying, "and now I have to wash my bedding, seriously..." 

There was no immediate answer from his mentor, causing Senku to sit back and stare at his phone. Was he... still going? There wasn't much noise...

"What... about you?" he questioned, almost feeling a ping of fear of what the answer could be. 

"What about me?" 

"You didn't, uh. Are you still going?" 

"Would you like me to?" 

Senku gave a deep sigh, irritation growing. This guy really needed to stop beating around the damn bush so much. 

Before Senku could quip back, Dr. X continued, "how about you tell me what to do for a change, Senku?"

It was a suggestion that made Senku's brain run blank, if only for a split second. He readjusted himself, not wanting to sit in his... mess... and placed his back against the wall once more. "Uh, okay. Keep... stroking then." 

Dr. X gave a small hum again, "All right."

 _Damn it._ Senku stared up at his ceiling, glaring at nothing but this whole situation. His afterglow had mostly left him, so his mind wasn't foggy, but he had absolutely no idea what to say or suggest. Without that fog, though, it allowed him to actually concentrate on the noises coming from his phone. He brought it closer - up to his ear, careful to still his own breathing to be able to really hear it all even more. The smallest hint of heavy breathing, the sound of skin against skin in the distance. 

Fuck. 

This wouldn't get either of them anywhere, though. The only thing he could pull from was prior examples. 

"What... do _you_ see, Dr. X?" 

"Hmm, are you trying to copy me?"

"Shut up! I'm just curious." It was followed by a few strings of curses, again in a language that his mentor probably didn't fully understand. 

Even so, Dr. X gave another chuckle to his outburst. "I don't usually care too much. How about... you tell me what to see this time, Senku."

The gulp Senku took was involuntary. If his dick wasn't so tired, it'd probably rear back to life. The first thought in his mind was the most obvious, but actually saying it was the hard part. He could probably think of something better, something less embarrassing, something _way_ less stupid, but only one thing floated around on his tongue. "...Me". 

"Oh? A face I don't know?" 

"Your eyes are closed or something!" Damn, this guy was toying with him, and Dr. X was the one supposedly being told what to do. Maybe this was still part of his game, all focus on Senku not knowing a damn thing about how to do any of this. Even through their messages, Senku was never the one actually giving commands.

"And? Where are you?" 

"I--" Senku had to pause, imagining his mentor sitting at his desk. Where would he be? Where could he fit in? "On... the floor, I guess. Between your legs." It was impossible not to see it as well, though perhaps in a different point-of-view from his mentor. Looking up, a face he couldn't place, but a body he had begun to learn. 

"Don't stop there, Senku... tell me, what are you doing?"

Shit. Senku began to shuffle again on his bed, becoming more tangled in his sheets at that point. "...just, jerking you off," it took a lot to say, his body feeling hot and flustered, and one again feeling even more frustrated that just saying a comment like that could trip him up so much. He heard his mentor give a small hum in response, though it seemed like a content one. He could give more though - swallowing his embarrassment, "You're, uh, trying to work on your own stuff. Your own research." 

"And you're beneath my desk, are you?" 

"Yeah," yeah... that was easy enough to imagine, and the idea of it all sounded sort of risky. Something you'd see in some teacher-student hentai. Senku cleared his throat, as well as his mind, "yeah, I'm there, being distracting."

"As you usually are." 

A quick scoff left the boy, "you're the one who answers back!"

A pleased hum came from the phone now - or was it a moan. The noise alone was nearly enough to drop the phone, but Senku held it tight between two hands now. 

"All right. Tell me one last thing then, Senku... are you pleasuring me with your hands?" there was a pause, a breath, deep but just so slightly shaky, "or, your mouth?" 

Senku... didn't have an answer, staring at the phone screen, minutes still counting away. His hand moved to his mouth, fingers gliding across his bottom lip slowly. He never once considered such a thing. Not for him, at least, but the image was there. The visions of the very few pictures he had gotten from his mentor flashing in his mind. If he was there, if _it_ was there, in front of him. 

His brows furrowed deep, hand now gripping tightly, "mouth," a single word, it was all he could even muster to say. 

Another hum came from his mentor, "perfect." 

The breathing was faster, sounds coming faster, even if distant. Senku quickly brought the phone right next to his ear again. Where there moans? If there were, he'd hear them. All of this was making his own cock feel eager again, just barely, but enough to reach down and slowly slide his palm against it. Everything still felt over sensitive, his legs beginning to twitch in response to it. The slightest of noises - a moan, a genuine soft exhale of breath - caused Senku's grip on his phone to tighten, not wanting to drop it, not now. 

There was a sudden vibration - a text? It didn't come from his own phone, but from Dr. X's, the sound passing through the speaker loudly. 

No, more of them, constant. A pattern usually consistent with a -- _wait-_

"Ah-" Dr. X could be heard moving around again, Senku hearing the squeaking of a computer chair. 

"...No, _no no_ ," Senku turned off the speaker phone, placing his phone against his ear, the entire thing feeling hot against his cheek from the constant use. "Hey - com'on, you _cannot_ be serious-"

"Senku," more shuffling, now some papers? "It seems there is an important call I must take." 

Senku tore the phone away from his face, only to check the time, quickly bringing it right back, voice loud, "It's like two in the morning there! What the hell?" 

"I _do_ have colleagues in other places."

There was no fucking way. "Wait, wait, at least--" 

Senku stopped dead in his tracks, fully taking in what he was about to do. To actually beg, for once _beg,_ but this time for someone to come on the phone just so that he could hear it..?! 

A laugh fell into his ear again, that same old delighted chuckle that had been plaguing his entire night. "Perhaps next time, Senku." 

The colors on the screen changed then to a darker hue. The call was dropped. Senku could do nothing but stare at it, watching as the green icon next to his mentor's name turned to a dull gray, signaling that he was no longer online. 

There was a lot of things he could do - the first thing popping up in his head being a very long and detailed message that his _dear_ mentor could wake up to, but instead he threw his phone onto his bed with perhaps a little too much vigor, the phone bouncing off and falling onto the floor with a small cluttering thud. 

All he could do was groan into his hands, soon letting them run through his hair. What a _weird_ phone call, and in the end it totally ended in Dr. X's favor, as per the damn usual. At least he got a good photo out of this. He'd have to save that one too, into that deep hidden folder. The words 'next time' repeated in his mind. He didn't forget them, not one bit. 

He had at least a week to prepare. 

* * *


	2. A Lot More Give

**Notes for the Chapter:**

> (dabs sweat off brow) so yeah uh here you go  
> i can't believe I've written over 25k in like two weeks for this
> 
> Thank you to everyone who's left a comment so far, every single one makes me just roll around and smile endlessly.

* * *

Senku always found the act of packing for long trips to be easy - there was such a simple method to it all. Then again, Senku was the type that could effortlessly pack supplies for a month long trip into two or three bags at most. The only hard part of it came from deciding which items to take or leave from his lab - especially when dealing with international travel. As carefully as he could pack the items away, it probably wasn't the best to bring any vials of corrosive or explosive liquids... 

Taiju was out front, enjoying the usual late afternoon television media. It was the norm, for the weekdays, for Taiju to be there, even if he usually just did his own things. In a way, Senku felt a bit guilty for letting him come over that evening, seeing as he was going to have to bolt off soon, and without really giving him a heads up at all. But Taiju was welcome to stay - he still had a key of course. Hell, he could even come to stay on the weekends now, if he needed. 

The passing thought of it all caused Senku to glance at his computer. A recent email still sat up on the background, signed as always by Dr. X, one that Senku had read but not prepared a reply to just yet. It wasn't just the need to pack that made Senku hesitate to quickly type up a response, but more-so the tone of the message itself. It didn't happen too often - the conversation taking such a sudden plunge into a subject that put Senku on edge. Maybe it was Dr. X finally showing his true colors?

The thought caused a tinge of prickling discomfort on the nape of Senku's neck, his hand quickly rubbing there to ease the feeling away. No, this man had always been a little skewed in the head to have this sort of ... 'relationship' with him in the first place. It was something else, something  _ off  _ in a more dangerous sort of way. At first it was quite rare, but now the conversation about chemical warfare or weapons of mass destruction popped up every few weeks or so. 

A sigh left his mouth, zipping up the contents of his bag. It wasn't a huge deal, in the end. Scientists all have weird ways of talking about the end of the world, how it'd happen, or how humanity could be totally wiped out in the blink of an eye. It's a shared common curiosity, and Dr. X loved to talk big. Senku had no problem telling his mentor he didn't give a damn about such things, and Dr. X never seemed to push the subject. In fact, Senku had an odd feeling that his mentor preferred it that way. 

Swinging the small bag over his shoulder, Senku leaned over to shut off his computer monitor. The unanswered email blinked off into nothing, only Senku's reflection staring back at him. He watched as his own eyebrows began to furrow. He could easily type up a proper email response on his phone on the way to the airport. The check in was soon - Dr. X could wait a big longer for a reply.

Besides, it wasn't a weekend.

* * *

It all felt like a blur, at that point. 

Senku sat, most of his energy spent, staring up at the slowly ticking clock of the airport terminal. 

Africa, Australia, back home for a week, followed by an array of more plane flights. At first it was all about the research of sulfa-drugs and an interest in fighting Ebola, but it was hard to stop there. The break before school starting back up again wasn't a long one, and Senku had been determined to fit as much travel as he could into the short period of time. 

He slowly began to browse the most recent messages on his phone. A myriad of messages from Taiju, as usual, all of them with typos and a lot of emoticons and exclamation points. The current message had something to do with seeing his crush at a department store. A tired laugh left Senku's chest - the guy was way too pure for stuff like that. 

There was also a full wall of messages from his father, every single one expressing excitement about his upcoming visit. It was Senku's next stop - a long plane flight to Houston, Texas, to meet up with his dad. The reason was simple, having totally maxed out the credit card he had gotten from his dad in the first place, the very last bits of it going to buy this exact plane ticket. The messages themselves talked enthusiastically about the things he himself was working on, excited to show all of them to Senku the moment he arrived at the Johnson space center. 

Senku didn't have the heart to tell the old man that he didn't plan to stay long at all. The flight back to Japan would leave that evening. It was at least enough time for a lunch, though. 

The final message that stayed currently untouched in his inbox was the most recent one from his mentor. 

Their weekend chats had mostly ceased entirely, at least any part that would need Senku to duck away into a private room, due to the drastically and constantly changing time zones. Their emails, however, continued as normal, as if nothing at all had changed. In fact, Dr. X had taken quite an interest in Senku's travels, encouraging him to begin his studies in pathological sciences and immunology. 

Senku flipped through the email now, eyes glossing over the words. Nothing of it was out of the ordinary, just the standard paragraphs full of formulas and discussing latest theories. It felt all too... normal. 

Did he miss it? The late night weekends that somehow became devoted to everything  _ but  _ science, despite what he would tell others. His weekends now were nothing but busy, free time going to writing his own journal drafts and passing out in hotel beds. There was no time to really spend on relieving any quick urges, let alone trying to find a time where his mentor was actually awake and willing to participate. 

Dr. X was incredibly understanding when Senku mentioned they couldn't message or even call like before, at least for a good while. Almost too understanding. Senku had hoped for his mentor to at least show a hint of being upset, even if it came in a passive aggressive email, or even telling him that he'd have to do something in return for ceasing their conversations. But nothing did happen, only a nicely worded email that was only full of hope and encouragement for Senku's studies. 

Stupid. 

That was probably his entire tactic, in the end. Act indifferent, and drive Senku absolutely insane. And there wasn't a damn thing Senku could do that wouldn't make him look desperate as hell. 

A rush hit him - sudden and bringing with it a surge of energy. Senku flipped back to the home screen of his phone, looking at the time. Yes - it was a weekend night right now in Houston. The times were perfect. Senku may have said that they couldn't have their long conversations during the weekend, but he never once said he wouldn't send pictures his mentor's way. The guy could benefit from a bit of teasing!

His eyes fell then on the large clock above the gate terminal. Boarding time was in twenty minutes. Not a lot of time, but enough. 

Senku hastily hopped from his chair, his carry-on bag tossed over his shoulder. It was hard to not grin to himself darkly, passing through the crowds of people, only one thought in his mind. Such an easy task - all he needed was a bathroom stall, and honestly he didn't even need to get hard. Just a good, risque, faceless picture to show Dr. X what he was missing out on. 

Senku turned the corner, working through the maze of confused people and their luggage, only to stop dead in his tracks at the sight of the bathrooms, his face falling now, showing off the effects of his jet lag. There was a large line outside the men's bathroom (and an even larger one outside the women's). A low, disgruntled sigh left his lips. Of course. It was the weekend. In an international airport. 

Senku's walk back to the gate terminal was slower, shoulders slumped as he mindlessly flicked through his phone once more. There was no other place in the airport that would give him a sense of privacy, at least not without ducking into places he shouldn't be. That plan was a bust, though in total hindsight it was probably for the best. He was going to Houston, after all. 

A sick feeling washed through his body as Senku sat back down in his previous seat, the crowd at the gate becoming much more dense now that the departure was growing closer. Houston. Where his dad was - but also where Dr. X was stationed. 

It wasn't a new revelation, Senku knew this entire time that going to the Johnson space center would put him in the exact same area as his mentor. But there was no real reason to ever bring that up. He never told Dr. X that his dad worked there, only that his dad worked overseas, hence the reason for constantly being home alone. And, unless his dad dropped his name constantly at work, there was absolutely no way... 

The sick feeling arose in Senku again, eyes closing as his eyebrows knitted, hand moving up to massage at the bridge of his nose. Okay, there was a massive chance that Dr. X knew that Byakuya was Senku's father. But, even then, it had never once come up in their conversations, and to actively seek out Dr. X without a single warning of him being in the same country was nothing but creepy. Giving him warning, though, was no better, only serving to make Senku seem desperate to meet him face to face. 

Senku sighed once more, hand now slowly moving through his hair, wanting nothing more than to get onto the plane so he could find the time to sleep. If at all possible, he could keep this visit as simple as can be. Stop in, see his dad, get money, get out, get on the earliest flight back to Japan. 

If anything, he could mention it all to Dr. X later. Maybe even tease the man on how he totally missed his chance at seeing him in person. 

He could always get another flight back.

* * *

The overhead shots of the Johnson space center obviously paled in comparison to the real thing. Overhead it looked like nothing but a mess of plain buildings, but on foot there were a number of things to look at. Luckily, Senku's dad had already passed warning to the gate crew out front that he would be visiting, which allowed him to aimlessly walk around the center with little to no one bothering him. 

Well, to anyone else it would seem like aimless wandering, but Senku only had one other thing he had wished to see, aside from his father. He caught eye of it from a good ways away, soon making his way up to the massive engine that stood on display. The Saturn F V1 engine, obviously now out of commission, but there for anyone and everyone to stand against it, comparing their own size. Feeling small against the massive machine was the entire point. 

There was a step behind him - easy to hear on the smooth pavement around the engine. The first panic in Senku's mind was having to explain to a guard why he was wandering around when not on a scheduled tour. The second sense of panic, one so much larger, became the only one engulfing his thoughts as the person behind him came to now stand next to him, not saying a single thing, only mimicking his gaze up towards the giant engine. 

It was...  _ not  _ his dad, that fact was ten billion percent true. His dad would have run at him, screaming the entire damn time. No, this person was slow, methodical, not saying a damn thing, only standing next to him silently as Senku tried hard to keep his own face calm and collected. 

Was he that obvious...? Did he stick out as a foreigner? The possibility of his dad snitching out his arrival was ridiculously high. Every fiber inside Senku's being was trying to avoid this sort of sudden meeting, wanting at least time to prepare, or at least think of something more proper to say. Sure - he had thought about meeting his mentor millions of times before, but actually being beside him--

Should he look over? Casually say hello, what's up, didn't plan on seeing you here?! What if this random guy  _ wasn't  _ his mentor, but just a random NASA employee, and he was totally overreacting? Why the  _ hell  _ was this such a sudden problem!?

Senku could only see the man out of his peripheral vision - just a dark blur on the very sides of his eyes. But he could notice him moving, digging something out of his pocket, before flashing it his way. The person was handing something over. 

It was like permission - as if that entire time, looking at each other's faces was still a forbidden act. But that simple gesture let Senku's gaze snap over, first seeing a single credit card clasped elegantly between two fingers, before finally tilting his head higher to see the dark eyes looking down at him. 

_ Smug _ \- it was the first thing that Senku could even think of when staring at the self-satisfied smile that was being shot his way. There was no mistaking it at that point - the man in front of him was his mentor, Dr. X, nothing but amused as always by Senku's presence. Dozens of other things flew through Senku's mind - his age definitely not over thirty, his clothing style didn't scream 'scientist' at all, height only about a head or so taller than Senku, his face was somehow pretty even with eyes that seemed to hint at a lack of sleep, and a smirk that filled Senku with nothing but annoyance... Yeah, this totally was the guy.

Tentatively, Senku raised his hand, eyes locking onto those of his mentor, slowly closing in towards the credit card held out his way. Was he silently offering to help with his studies...? Was there  _ really  _ no catch to this?

No - He had pulled the card back, smirk growing more twisted before suddenly washing away for a more soft, warm expression. "Your father tells us that you have already maxed out his credit card." 

Senku's eyes quickly narrowed up at the man, mouth beginning to twist. It wasn't as if he needed more proof, but hearing his mentor's voice, the one that he shared way too many nights listening to through a phone, come from the person in front of him... 

There was no  _ actual  _ need to panic. It was bound to happen someday, especially when Senku had no plans of staying in Japan at all, knowing full well he would travel just as he was doing then. His interest in space exploration was destined to make him meet up with this guy someday, a thought that always swirled around in his mind (sometimes at the most improper moments), but throwing himself into a sudden bout of anxiety wasn't going to help him one bit. 

So he sighed, regaining what composure he could muster up, ignoring every neuron of his brain that was trying to make him remember their late night conversations. "Yeah," he said, voice full of nothing but irritation, a tone more focused on himself but it could easily be read as animosity for his father throwing his name around so carelessly. Which was, also, completely true in that moment. 

Then again, it wasn't as if his father knew he was sharing emails, and  _ a lot  _ more, with one of his colleagues. Probably best to keep it that way. 

Senku watched as Dr. X slowly twisted the credit card in his hands, head slightly tilted as if lost in thought. It created a slow rising chill in Senku's body, knowing there were only a few things this guy could be considering, and only a few of them consisted of casually talking about his scientific travels in the cafeteria. But that wouldn't call for a need to be lost in consideration - he knew that look all too well, being a look he often wears himself. His mentor was debating something, something that had a lot of other outcomes. 

"Right," Dr. X said then, pocketing the credit card and turning, all processes of consideration seeming suddenly complete. "Did you tell your father that you had arrived, yet?"

Senku's stare only narrowed again, "No, not yet. I wanted to look around first." 

"Good, don't," with that, Dr. X turned, hands in the pockets of his coat as he began to walk away from the massive engine and towards the main group of office buildings. There was never a command to follow, but Senku found himself in a hurry to do so, quickly falling in step behind the older man. 

There was an urge in him to ask why -  _ why  _ was it important to not tell his dad that he had gotten here yet? Besides, some other people had seen him walk about, and the main gate had a record of him being there, it wouldn't be hard for his dad to figure it out. But there was no real point in asking that question. The answer was becoming obvious, as they passed wordlessly into the back doors of one of the many office buildings. Wherever they were going, it wasn't anywhere densely populated. In fact, it was eerie, Senku not seeing a single person as they passed through large labs and hallways.

"Ah-" The realization hit as Senku peered into one of the many rooms, taking just a moment to stop and look at the ripped up floor tiles and bare walls. "This building," he said it while quickening his pace again, soon falling back behind Dr. X, "is it under construction or something?" 

His mentor gave a hum, followed by a single nod, "This floor, as well as the floor above on the south side - a remodel. Until finished, most offices have moved to other floors and buildings. Ah," Dr. X's face turned back now, eyeing Senku with a dark grin as he continued to walk forward, "aren't you the lucky one, Senku?" 

Senku could feel his shoulders tense, partially unsure what he meant, but a gut feeling sending him in the right direction. Even so, Senku only sent the man back an annoyed stare, " _ why? _ "

"You've arrived on a weekend." 

"Yeah...?" Senku could feel his face heating up, something entirely out of his control. It only made his brows furrow more, there was no question that this guy was toying with him. It's all he ever did. His reaction seemed good enough for Dr. X, Senku watching as his gaze turned back forward. 

"No one around, even the construction crew is off for the day. Aside from the few who work on the floors above, this area is nearly abandoned. And only on this day of the week." A hand rose from one of his pockets, gesturing to the building around them, "it's almost like you planned this." 

Senku could only scoff, "You really think I chose a day to visit where some random construction was going on - but  _ also _ when they'd all have a day off? I just chose a close and cheap flight." 

A laugh came from Dr. X, his shoulders shaking slowly, "Yes, I know. Which is why," he had stopped then, coming to an seemingly ordinary door. Nothing about it stood out from the others, aside from a nameplate being taken off from it, but that was an appearance it shared with many of the office doors that Senku had seen. Either way, this seemed to be the destination that his mentor was looking for, his hand falling on the handle and gripping tightly. "You're quite lucky. That is all." 

He walked inside, offering no invitation for Senku to follow, but he knew he was to do so anyway. The door was held open for him, allowing him to enter, looking around and fully expecting an office to be staring back at him. But this... 

Senku's energy was leaving his body, arms feeling heavy at his sides, "a bathroom?" It was basic, nothing too stunning, even for a NASA branch building. A large counter with a row of sinks, large mirror, as well as the usual stalls and urinals. Luckily, it looked clean, but that didn't excuse the fact that it was a  _ bathroom _ . "I at least thought you'd bring me to your office..." 

"Oh?" Dr. X closed the door, looking to Senku with a delighted smile, "so you can sit beneath my desk? You  _ do  _ like that one."

"What?!" Senku blurted it out, hands quickly coming up to rub at his face as if it would cause any redness to settle down. "N- _ no _ , I just- I mean bringing me into a bathroom is sort of..." He stalled in the attempt to find a good enough word for it, despite the dozens coming to mind. Cheap? Creepy? Uncaring? 

But, a hum from his mentor closed off his thoughts, "My office is in a space I share with others, currently. This includes your father. I do not think you'd wish to go there." 

Senku quickly began to shake his head, but his face only felt hotter. Dr. X wasn't outright saying it, not exactly, but it was obvious why they were in this room. He knew it following him, he knew it as soon as they began to talk about this floor being barren of people, but there was no use in thinking otherwise now. 

"Most other rooms around here have been ripped up, as you saw, but this bathroom still sees daily cleanings. So you'll find this room much more sanitary than anywhere outside," he said it a tone that suggested such a thing should be obvious to Senku, "also, of course," his hand reached down towards the handle, twisting the simple lock there, "this is the only room with a proper lock."

"Ah." 

Dr. X walked back to him now, standing in front of Senku and causing the younger boy to press his back against the sink counter. 

"Hmm, you're quite red in the face, Senku."

Senku found himself only able to glare once again, having trouble now keeping eye contact with his mentor's unblinking and unwavering stare down at him. He wasn't even that much taller, but Senku couldn't help but feel small against his frame. "Yeah?" At least his voice wasn't dripping with anxiety, "you just locked me in a  _ bathroom. _ " 

The stare down at him changed then, Dr. X holding one of surprise, quickly glancing towards the bathroom door, "Yes, from the  _ inside,  _ Senku. You can leave any time you want," he turned back then, the façade of surprise gone, replaced with a twisted smirk, his hand moving up to lay against his cheek as if he was pondering a thought, "you  _ are  _ the one that followed me all the way in here, on your own accord." 

Senku quickly opened his mouth, ready to throw a retort back at the man, but closed it just as fast as he glanced away, glare now directed at the floor. He was right - Senku knew the second he started to follow this man that they'd most likely end up in a place like this, and yet he eagerly found himself following anyway.

"Why did you follow me, then?" 

"You waved a  _ credit card _ in my face?!" It was partially the reason, at least it was the initial reason his curiosity was piqued in the first place. He watched as his mentor's head began to tilt slowly, looking down at him with skepticism. 

"Yes, but you also came to Houston to claim more money from your father. You do not  _ need  _ more money from me."

Shit. Senku inwardly cursed, his glare not leaving. His mentor was doing nothing but toying with him. Dr. X was holding that smug smile again, a single step forward pushing their frames together, making Senku quickly lean back and brace his hands on the counter top.

"You followed me," two hands were placed on either side of his body, trapping him there, causing Senku to quickly look to the side, unable to stare into that face. "All on your own, your mind racing with what may happen. You even thought I was bringing you to my office, imagining we'd be alone. You could have turn back at any time, feigned a message from your father," his face was  _ closer _ , his hand coming up to take Senku's chin between to fingers, propping it up to look him in the eye, "and yet, here you are, making such an angry face in an attempt to pretend that you do not want to be here."

Senku's brows knitted, eyes closing as he tore his chin away from Dr. X's grasp. He, too, could play this smug game, side-eyeing him with a stare of contempt, "is this amusing to you, too?"

The smile that met him was warm, perhaps too warm, "yes, very." 

Senku began to tap his fingers against the counter top, sighing softly, "you've never told me  _ why. _ " 

He got no real answer from his mentor, only a small questioning hum. He needed to give more, if he actually wanted a response. With a deep sigh, Senku turned his gaze fully back to Dr. X, crossing his arms and finding a bit of comfort in the small defensive wall it created. "You're always saying that, but you've never once even explained why you find me so amusing in the first place. It's just some baseless compliment."

Dr. X stared down at him, for once seeming to be at a loss for words. But his face quickly twisted, eyes bright with excitement, "Senku, I never took you to be the type to actually fish for praise! Are you asking me to list off the things I like about you?"

"What--  _ No!" _ Senku's words felt caught in his throat, choking them out, "I am  _ not  _ doing that, I'm just..." he looked down at his crossed arms, entirely perplexed on what his intentions actually were. Maybe his mentor was right. What the hell. "I'm... making small talk?" 

There was always something bigger, wasn't there? First Senku finally got a handle on their escapades through messaging, but only to be thrown off guard when thrust into voice calls. Now, when those late night calls on the phone were becoming something he had more confidence in, they just  _ had  _ to meet in person, in a damn bathroom, where Senku had no idea what to say despite running the scenario through his mind millions of times. 

But, when looking up, the face that looked down to him was soft, his mentor once again moving his hand up to cup at Senku's chin. This time, the grip was tight, keeping his chin in place as their faces grew closer together. Senku began to lose sight of most of the features of Dr. X's face, but he could still see his eyes, staring down at him, dark and unblinking. It was no longer a soft stare at all. Something about it made Senku's body feel cold.

"You're eager, Senku. You're also smart, too smart to not have known," the hand left his chin, only to ghost its fingers across his jawline, soon meeting his neck. The touch was so gentle, compared to the intense stare, making Senku tightly close his eyes, unable to focus on it. Just his stare alone felt invasive, studying him  _ too  _ closely. "You've known for a long time, perhaps since the beginning, and yet you sent every single picture with so much enthusiasm." 

Senku was unable to see, but he could feel Dr. X's other hand slowly move to his torso, gliding beneath the rim of his lab coat collar, before both hands were at his neck. In a quick, jerking movement, the hands took his jawline between them, forcing his stare up once again, holding his neck in place. It was enough to rock Senku's stance, stumbling slightly and grabbing on to both of Dr. X's arms for support, staring up at those dark eyes. He was close still, close enough that warm breath fell on his skin. 

"In the end, Senku, you are just a smart, undisciplined boy, who can't find it in himself to admit that he is a needy slut." 

Senku found himself gulping, eyes darting quickly between the two that stared down at him, his entire body now feeling uncomfortably warm. There was no response to be found in him, unsure if the comment terrified him or turned him on, though the chances were high it was a mix of the two. He flinched - feeling the two thumbs on either side of his jawline begin to caress at his warm cheeks, unable to tear his gaze away now. 

He could still feel his breath, so close, making the air between the two of them warm. There was...  _ no _ actual way a kiss would happen. It was stupid to even consider such a thing. But even so, Senku's own lips began to part, grip turning tight on his mentor's arms, unsure if he wanted to speak or how to even lure in such an act. 

But Dr. X only smiled, letting go of Senku's neck, only to have both hands fall down slowly and begin to undo the top button of his lab coat. It allowed Senku to let out a shaky breath, eyes closing as the acceptance of doing this in the  _ bathroom  _ clicked. Actual intercourse, or at least something close enough. With his mentor. 

"You sure have a wonderful gift in picking where to do these things," at least his snark still came naturally. 

"We just spoke about this - do you have a better place in mind?"

"It's clean, I  _ guess. _ "

Another button undone, followed by a chuckle from the older man. "We could risk it, if you wish," his hands fell to another, working slowly, "perhaps it's a lunch break, you could sit in my lap. You'd fit quite nicely. Though, it would be an awful lot to explain, when your father walks in." 

Senku scoffed, "I know, can we please stop bringing up my  _ dad  _ while you're undressing me?" 

Dr. X only hummed, finally having finished, eyes glancing back up to him, "this is for the best, in the end. Since there is rarely someone wandering these parts of the building, you can be as loud as you need." The lab coat was being pulled from him now, placed on the counter beside them, still leaving Senku feeling overly warm. 

Noises, at home, those were easy to deal with - in fact it wasn't hard to even fake them a bit, make them nice and loud just to carry more over the phone. But it was always his own hands, his own pace, and no one home at all. Never loud enough to alert his neighbors, of course, he could never leave his apartment again if that was the case. This building wasn't as barren as Dr. X was making it seem, there were still other floors, and sound carries dreadfully well though empty rooms and hallways. 

Senku took a deep breath, knowing full well he'd just have to keep those noises in check. He looked back up, into that smug smile that knew for a fact that Senku had no desire to leave at all, and gave another scoff. Dr. X may be able to lead whatever this was, but Senku wasn't going to sit back and do nothing. He raised his hands then, fingers tangling in his mentor's tie, undoing it before turning his attention to the small buckles that sat above it. 

The action caused the older man to pause his own movements, a look of surprise arising for  _ just  _ a moment, before resuming the same smile he held before, that look of pompous amusement. Still, Senku caught it, pride tugging at the corner of his lips. His mentor's arms fell a bit, staying still at his sides as he allowed Senku to continue, dark eyes watching as Senku's hands slowly fell on each button to undo the dark lab coat. 

Once done, Dr. X shrugged it off, taking a moment to place it as well as his tie and little collars (what were those things, anyway?) alongside Senku's lab coat. His attention quickly resumed back on Senku, though, hands grasped at the younger boy's waist, gripping tightly at the fabric there. 

"Up."

It caused Senku to blink - a demand that made no sense at first, but he soon quickly caught on, leaning back now onto the sink and soon using his arms to lift himself to sit on the counter top. He positioned himself in a spot between two sinks, just enough room for him. He was taller then, eye height now level with the man in front of him, able to finally feel on equal ground in that regard. But Dr. X was not staring back at him, instead his gaze was focused downward, wasting no time in undoing Senku's tie as well as the buttons on his undershirt. There was less stalling now, less words to tease him, only two warm hands that ran against his torso once the buttons were all undone, causing a hitch to Senku's breath. 

In a quick attempt to not feel all the focus on himself, Senku's own hands pushed forward, reaching up to trace the jawline of the man before him, unsure entirely why the desire to do so had filled him. His skin was soft, warm beneath his finger tips, and Senku's hand slowly moved to cup the cheek there. 

The stare that met him was... off guard. Dr. X had ceased his movements entirely, staring back at Senku with wide eyes, eyebrows high. It was the first time Senku had seen  _ that  _ expression, though the way he held the stare seemed like it was one he rarely wore in the first place. It didn't stay for too long, Dr. X's eyes soon creasing into a smile, his own hand coming up to take Senku's, clasping it into his own. 

His face was close again, but his tone stayed warm, kind, "there are times, Senku, where I worry that you are too soft for me." 

"Eh--?" Senku had no time to question the strange comment, his lips suddenly feeling  _ warm _ , a pressure against them caused only by his mentor's own mouth. His eyes widened - lips straight, able to recognize exactly what it was but unable to react properly at all. The air in his lungs felt trapped, too anxious to breathe out - do you breathe during a kiss? That's what this was - a  _ kiss.  _ Obviously you'd have to breathe, or else both parties would probably lose consciousness pretty fast, but what was even customary? Nose breathing? Or just gasps when lips fell apart?! 

The kiss broke, only for Dr. X to tug on Senku's chin, forcing his lips to part. "You really  _ do _ act like a child at times," he teased, quickly pushing their mouths back together, this time Senku feeling his mentor's tongue invading his mouth. 

It brought his breathing back with a quick gasp, at least, his own eyes now finally shutting tightly as a shuddering noise left his throat. The thought of whimpering against Dr. X's tongue was too embarrassing to focus on, Senku instead trying to follow along and match his mentor's movements, his mouth filling with the taste of black coffee, strong and bitter against the back of his tongue. His hands grasped at the shoulders in front of him, fists full and tugging on the fabric there, more noises hitching in his chest as he felt Dr. X's tongue slide across his lips, teeth just barely grazing against them. 

It kept clicking at random intervals - a kiss, with his mentor, the same person who's face he had been forbidden to see for years. Everything given to him by Dr. X up until that point had been more or less methodical, even in terms of risque pictures and late night calls. There was never really a sense of affection, only bemusement and satisfaction. Senku knew very well he fed his mentor's ego and lust. But being kissed - the back of his neck being held so gently by Dr. X's hands, pulling their mouths together, pulling their bodies more flush. Maybe it was because it was Senku's first kiss, but he couldn't help but desperately want something more out of it. His first kiss, on a damn bathroom sink. Though, it  _ was  _ happening at a NASA branch - that was worthy of bragging, at least. 

Dr. X's hands, which were once so slow and meticulous before, had become feverish and quick, taking Senku's shirt from his body and letting it fall haphazardly into the nearby sink. Senku couldn't find it in himself to care, it wasn't as if some water would hurt it, and besides, there were hands now roaming his torso, nails gently gliding across his skin before beginning to dig in his more softer areas, causing him to shudder and exhale sharply into his mentor's mouth. The whole breathing thing didn't become easier, the kiss staying deep and constantly causing Senku to pull back, desperately needing oxygen, only to be brought back into it seconds later. 

There was a tug to his belt, the buckle easily being undone and loosened. It was all going so fast now. Senku's own hands tried to keep up, pressing his form flush against Dr. X's as he reached down to undo the older man's belt as well. Their mouths parted then, his mentor running his lips across Senku's jawline and allowing him to finally breathe normally. 

His cheek was being cupped, a kiss so gently placed against the shell of his ear, Dr. X whispering softly to him, "stand for me". 

Senku did, not questioning the request at all, sliding off from the counter. Dr. X didn't move back much at all, causing their bodies to press against one another, bare chests touching and alerting Senku promptly to how much his body was already sweating. Their height difference was more obvious then, Senku's lips pressing against his mentor's collarbone as the older man's hands gently slid down his torso. His pants were being fully undone, pushed from his hips, beginning to now fall on their own and gather at his thighs. 

Senku expected his briefs to come next, mentally prepared for it, to be bare in that way for his mentor, but instead a hand came to cup and grind against the growing erection there. His body went rigid, a shaky breath falling against Dr. X's chest, Senku soon hearing a chuckle vibrate against him. 

A kiss fell to his temple, "such a sensitive boy." Senku could feel the lips against his skin twist into a smirk. 

"Shut up," it barely came out from him, voice cracking as it did. Senku could feel his mentor's fingers hook into his briefs now, his eyes closing as they slid down his hips. His eyebrows furrowed, feeling his cock become free. It wasn't as if Dr. X hadn't seen it before, but the feeling of being exposed was still causing his body to feel tense. 

"Up, now," the whisper fell against his temple again, this time causing a shudder to run up Senku's body. 

He listened, lifting himself up like before, this time quickly noticing how cold the counter top felt against his bare skin. But lips falling against his neck distracted him from that, his eyes closing as he tangled his grip into his mentor's shirt. Dr. X's hands, so warm, traversed his body so effortlessly, nails showing their dominance at random intervals, right in the spots that could cause Senku to forget his promise to himself to  _ not  _ make loud noises. His mentor's mouth, just as hot, bared teeth against his throat before suckling there, causing marks that made Senku appreciate the high collar of his shirt and lab coat. 

Now that his pants and briefs were mostly off, it was easy for Dr. X to pull them further down Senku's legs. Senku didn't fight it one bit, letting the older man undress his lower half, not complaining even as shoes were taken for ease of removing his clothing. Senku found himself nuzzling his way into his mentor's neck, enjoying the scent there perhaps too much. Cologne, or maybe it was just the smell of sweat and bodies, Senku couldn't be sure at that moment, but he couldn't help but find the smell appeasing. 

The hands were moving back up Senku's legs now, gliding slowly across his thighs, thumbs dipping between his legs. They gripped tightly, the thumbs of his nails digging into Senku's inner thighs, pulling and forcing them further apart. Senku's breath felt shaky, every nerve feeling like fire beneath his mentor's touch. His hands were  _ right there _ , so close, just a bit further - if Senku raised his hips then Dr. X would get the idea.

But, that would be giving in too fast. Senku needed to regain his composure, regain a bit of control over the entire situation. He raised his arms, wrapping them around Dr. X's shoulders, able to now run his own hands through the back of his hair. "Don't you think... this is a bit unfair?" Senku's own voice surprised him - deeper than usual, but somehow barely over a whisper into his mentor's ear. 

But Dr. X didn't stop his movements one bit, his hands still teasingly wandering his thighs, responding only with a hum and teeth grazing the shell of Senku's ear. 

Senku could feel his lips curling into a grin, but none of it could be read as happy, only growing irritated. "You do realize you have me down to my damn socks, and you still have everything on?" He let his face leave the crook of the older man's neck, chin now resting on Dr. X's shoulder as he gazed to the nearby sinks filled with their clothing, "aside from what, your coat and a tie?"

Dr. X pulled away then, only enough for their faces to be in each other's view, "It's not a requirement, is it?" 

'I-...  _ no _ ," Senku gave a sigh then, eyes closing as his brows furrowed. "It's not for  _ me _ , either," it wasn't as if Senku had a lot of  _ experience  _ in these things, but as far as he knew, public sex usually didn't require getting completely naked. 

Dr. X only gave an inquisitive hum, pulling their bodies away more, now to give a glance down at Senku's body. Senku regretted it, in that moment, even mentioning anything at all, the urge to press his knees together to avoid being ogled at, but unable to do so with the position they were in. Even his ears felt hot in that moment, grip tightening again on his mentor's shoulders, hating how his dick twitched happily at the idea of being on show. 

"I like seeing you this way," Dr. X said then, causing an eye roll from the younger boy. 

"Right, yeah, half naked on a bathroom counter?"

It happened quickly - Senku's hips were grabbed tightly, nails digging as they were pulled forward. He nearly lost his balance entirely, arms snapping behind himself to brace against the counter top. He started to shout out a quick " _ Hey _ \--" but his voice was quickly broken by a shaky gasp, hips crashing into his own. There was an obvious hardness in his mentor's pants, still sealed away, pressing hard against Senku's groin and hips rolling in a purposeful attempt to grind hard against Senku's eager cock. 

Dr. X's entire body had moved closer, enveloping Senku's form, his ear once again being hit by hot breath. "You look quite helpless, this way," his mentor's voice was low, a husky rumble in it making Senku bite at his lips to deny another whimper that threatened to leave him. 

Instead, Senku gave a nervous laugh, trying hard to gulp it down. His legs were only being pushed wider apart by his mentor's close proximity, knees essentially wrapping around the older man's hips. His dick was hard, almost concerning so with how little it had even been touched at this point, twitching and desperate for attention against his stomach. The slow grinding of his mentor's rough pants against his sensitive skin was  _ not  _ helping. 

But the grinding didn't last - his mentor soon moving just far away enough for their bottom halves to no longer touch. "Well?" Dr. X asked, bringing his face away to also stare inquisitively down at Senku. "You're going to complain about not being equal, and then not do a thing about it?" Something about his stare was dark, the bags under his eyes creasing into a grin, nails digging again at the softer parts of Senku's hips. 

Senku felt his brows knit together, gaze flowing down the body in front of him. Dr. X's shirt was open, revealing a single line of his chest, but as much as Senku wanted to slide the garment from his mentor's shoulders, he knew that was not the most important part, here. Licking his lips - a subconscious move that only showed the height of Senku's nerves, he moved his body and hands forward, undoing the buckles there. He could feel his mentor's stare, curiosity causing him to glance up only for a moment to see the small smile directed his way, before hastily throwing his attention back to his working hands. 

As soon as the pants had slack in them, Senku's hands trailed the rim of the pants to the outer points, finding the time to enjoy the smooth skin of his hips. It wasn't much, but Senku watched as his mentor's stomach quickly shuddered against the touch, a reaction Dr. X probably had no control over. It caused a small but sudden surge in Senku's body, wanting nothing more in that moment than to run his mouth along the skin there, eager to get more of those small shivers. 

But Dr. X had other plans, a whisper in Senku's ear urging him along, "take it out." 

Senku gulped again, nodding along to the order, one of his hands gliding fingers along the elastic rim of Dr. X's briefs, tugging them a bit to allow his other hand to slip inside. There was an intense warmth inside, fingers and palm slowly grasping his mentor's cock and sliding it out. It was almost stupid how much seeing it sent a wave of excitement through Senku's body. In his hands, finally, the same one that he could only view through a couple angles through rare hidden photos. So hot against his fingers, the weight and girth and even the color of it entirely different from his own. 

There was a nuzzle against his ear now, his mentor's face tickling his skin, lips grazing his cheek. "Good boy..." 

The words sent a shiver up Senku's body, a heavy and audible breath leaving him. His mentor moved closer again, their hips soon flush together, the heat of his mentor's cock soon falling against his own, both lengths pushed against his stomach as they slid against one another. Their size difference was more obvious to him now, though Senku already had a good assumption as to his mentor's size from the images he had received before. Even so, having it pressed against his own, his hips nearly shaking with the need to rut and grind against his mentor's...

"Senku," his name, so soft against his skin, Dr. X's fingers ghosting gently across his thighs. "If I told you to touch yourself for me, just as we do on the phone... I can't help but wonder what sort of show you would put on for me." 

Senku's entire voice felt gone at that point, nothing in his throat signaling that any words would come out even if he tried. His gaze was locked on the way their skin slid and rubbed with each small movement. Dr. X was so hard against him - even without being teased or touched.

"If I told you," Dr. X's voice was deeper now, registering almost as a growl, his hand coming down to wrap around Senku's fingers, bringing the boy's hand up higher, "to stick your fingers deep into your mouth," it was followed by Senku's fingers now being pushed against his lips, the tips running along his tongue, filling his mouth with the the slightest taste of salt. "And, told you to stretch and ready yourself in front of me, would you be willing to obey such an order?" 

Senku's fingers were being forced into his mouth at that point, but he wasn't denying them entry, eyes closing as his tongue began to run against them. This wasn't the first time, though it was definitely the first time his mentor was controlling how deep his fingers pushed. He'd be watched this time, the act of envisioning it something he couldn't control, series of images and fantasies flashing--  _ Wait.  _

Senku stopped, brows furrowed and eyes wide as he tore his face away from both his hand and Dr. X's grasp, other hand now coming up to grab at his mentor's wrist. "Hold --  _ Hold on a second- _ " his voice sounded frantic, matching the sudden bout of apprehension welling up in his body. He watched as Dr. X stared back at him, his own expression seeming a bit shocked, brows knitted and gaze examining him carefully. 

It took Senku a second to gather his thoughts and clear his mind, letting go of his mentor's hand as well as taking back control of the one that was just knuckle deep in his mouth. He held them up, as if creating an imaginary barrier between the two of them. "Where is this going?" 

The look he got back in return was intense, his mentor's mouth slightly agape as a single eyebrow rose, head tilting a small angle. It was a stare that was, quite literally, calling him an idiot. 

Senku quickly began to shake his head than, hands waving, "No -  _ no _ , damn it, I mean," he sighed then, eyes closing as he breathed deep, "Look, I don't think you're  _ that  _ much of a weirdo to be carrying lube in your back pocket." He began to look around then, not expecting there to be a magical bottle of lube in the bathroom, but only doing so to prove a point. 

His eyes fell then on a small bottle - soap most likely, possibly lotion, the writing on it in some fancy English cursive that Senku had trouble making out. The only emotion that filled him at that point was pure terror, the idea of some mystery lotion filling his insides. He reached out then, hand wide as he slid the entire bottle from the counter, knocking it off the side and hearing it fall to the floor with a slight thud. "No." 

Readying his case, he looked back to Dr. X, mouth open to rebuttal against anything the older man had to say. But his mentor only looked down at him with a warm and bright smile, eyes much brighter than before, the stare almost feeling eerie with how different it had been from every other expression Senku had gotten that day. Actual utter affection were the only words that could come to Senku's mind. 

"Are you a cat...?" his mentor asked, eyes still bright.

Senku could only glare, quickly scoffing, knowing full well now that this was only a ploy to tease him even more, "will you stop that, I'm serious!" 

But Dr. X only gave a low chuckle, his smile still kind as his hands took both of Senku's into his own, his grasp on them gentle. "If you will not prepare yourself, then I'll do so." 

"Wait-  _ what? _ " 

"Up," he said it while raising Senku's arms high, "on your knees." 

Senku paused a moment to stare intensely at his mentor, "On the  _ counter _ ?!" 

"Yes, turn around slowly." 

Senku stared at the older man, waiting for a laugh or a shake of his head to tell him that he was only joking. But there wasn't a single ounce of uncertainty in his face, only that simple smile and waiting eyes. An eventual and long sigh left Senku, gripping more steadily onto his mentor's hands to steady himself as he slowly managed to bring his legs fully up onto the counter. It took some maneuvering, especially in attempt to not look clumsy or idiotic, before Senku could actually turn himself around and sit on his heels, facing the mirror - _ Oh. _

He was facing the mirror - his view now completely full of himself. His skin red and blotched in places, small bruises on his neck already showing, his hair a mess and half falling down in multiple places. Behind him stood Dr. X, staring over his shoulder with hungry eyes.  _ Hungry  _ \- it was the best word Senku could find for it, watching as his mentor's pale hands wrapped around his waist, the older man's face soon entering the crook of his neck. 

All Senku could do was watch, there was literally nothing else for him to look at, feeling his mentor chuckle against his skin as those hands slid down his body. One of them rested on his thigh, a gentle pull able to tug his knees further apart, the other sliding fingers teasingly across his cock before engulfing it in a tight grip. A broken breath left Senku, blinking hard as he watched the hand slowly begin to stroke at him. 

"You wanted to know where this was going, Senku?" Dr. X pressed his face against Senku's temple, his breath hot against his clammy skin. He couldn't answer at all, instead beginning to lean back against his mentor's chest, hips beginning to roll along, already desperate for something more. His eyes flickered up to watch as Dr. X began to trail his mouth down his jawline, soon moving back to kiss at the nape of his neck, teeth grazing as if threatening a bite. 

"I am going to fuck you," the kisses began to move down now, slowly falling against Senku's spine. He was no longer able to see Dr. X, but he could watch as his chest began to arch on its own at the sensation of his mentor's lips trailing down his back. "While you watch yourself in that mirror. And, you..." he paused then, his grip on Senku's cock suddenly leaving, both of his hands grasping at the sides of Senku's hips, "are going to try not to scream out, to the best of your abilities." 

His face was visible again to Senku, peering over his shoulder, "now, brace yourself against the mirror."

Senku's brows quickly twitched down, not understanding but still following the order, having to lean forward a bit as he pushed both of his palms against the cool glass. It was a good thing he did so, his hips suddenly lifted upward, an act that jutted his torso forward and into the mirror as well. 

"Hey?!" His entire chest was pressed against the glass now, head turned to the side as he looked back at his mentor. It didn't take much brain power to see his ass was now more level with the face behind him, irritated glare soon morphing into one of pure horror as he watched both of his mentors' hands begin to spread his cheeks wide. 

"What the HELL are you doing!?" The words spat out, even if Senku very well knew the answer. As expected, Dr. X didn't look up at all, thumbs caressing the plump skin. 

"I told you," he said then, one of his fingers slowly tracing down the crack, soon giving a small press against the hole there, "that I would make you ready for me, do you not remember?" 

Senku inwardly cursed, looking away quickly, eyes screwed tightly shut as he pressed his forehead against the cold mirror. There was no way he couldn't focus on it, his knees feeling shaky and sore against the hard counter top, body giving a jolt as he felt a cold wetness fall against him. 

Spit - he must have spat, right onto his hole, the thought of it sending another chill up Senku's spine. It was soon met again with a finger, playing against him, pressing gently enough to entice a sudden whine from the boy, but not enough to actually enter him. 

It was fine - this was  _ fine _ . He had done this before, many times, though usually his mentor was thousands of miles away, only connected to him by a voice call, enjoying himself too much by just listening. It was, technically, nothing new to his body, only new in the sense of a different person's hands doing the work, and in a position to be able to view him  _ way  _ too intimately at the same time... 

Very slowly, Senku could feel a single digit enter his body, slick with spit as it reached deep. Senku controlled his breathing, knowing full well that tensing his body would only get him scolded. He could hear a hum behind him, no idea what it could mean, but only assuming that his mentor was enjoying this somehow. The embarrassment and shame washing over Senku's body with each thrust of the finger kept threatening to tense his body, hot breath against the mirror making it fog around him and cause sweat to drip from his cheeks and nose. 

"Do you want to touch yourself as I do this, Senku?" It came from his mentor so nonchalantly, as if none of this was super humiliating. "You're entirely welcome to." 

A quick gulp left Senku, his hand reaching down, feeling unbalanced against the mirror, palm enclosing around his cock. His strokes were soft and slow, afraid to go too fast and tense his muscles. The single finger inside him changed to two, twisting and scissoring inside him as they moved from and back into his body. 

Senku couldn't deny it felt good after the initial feeling of evasiveness left, Dr. X's fingers able to probe much deeper than his own ever got. His hand against the mirror flexed against it, fingers desperate to dig into something, the heat from his body creating more blotches of fog on the glass. But, just as his hips had begun to sway against the rhythm of both his mentor's fingers and his own hand gently pumping at his dick, the fingers behind him removed themselves entirely. 

Senku took it as a moment to calm himself, stopping his own movements as well and steadying his breath, knowing Dr. X wasn't done yet. 

But the expected fingers did not meet Senku - only something much wetter, slick, moving against his crack and firing off a number of alarms that caused the boy to jut his hips forward, tearing them away from his mentor's grasp. He looked back then, flush now creeping down to his shoulders as he shot a glare towards the man behind him, watching as Dr. X looked back at him with half lidded eyes, wiping slowly at his mouth. 

"Are you serious...?" Senku said, voice low and full of disbelief.

"Were you not the one just saying we have no lube?" 

Senku narrowed his eyes, studying the way his mentor's eyebrows raised, the older man knowing full well that he had no true argument against this. His glare turned deeper as Dr. X's mouth slowly twisted into a smirk, not waiting for Senku to turn back around before spreading him wide again, face moving closer to his body. 

Senku tore his gaze away, back to pressing his forehead against the mirror, eyes shut tightly and hands braced against the glass as well. He  _ could  _ say no, fuck this, there was no actual way he was going to sit still as his mentor shoved his  _ tongue  _ up his ass, but his knees stayed locked in place, sore against the counter top, toes curling as wet fingers began to press and pull at his hole. 

The sensation was back again - wet and slick, Senku breathing as deep as he could before letting out a slow and shaky breath. He never, ever, once pictured Dr. X as the sort of person to be into this sort of thing, but it wasn't the first time his mentor surprised him with new things. Senku tried hard to turn off his brain, a nearly impossible task for him in the first place, made harder by the wet muscle slowly teasing him. This was just teasing, in the end - he knew it, nothing more than a way to make Senku squirm. Even so, Senku could do nothing but let it happen, breathing already ragged with small whimpers each time he felt the slick form push deeper inside him. 

It was stupid how good it felt, continuously making his thighs shake and his dick twitch happily between his legs, a long stream of pre dripping onto the counter beneath him. Senku knew this wasn't actually doing much to lube him at all, but it didn't seem to really matter to Dr. X, the tongue still flicking deep and Senku's moans still escaping in small whines. Thankfully for Senku's sanity and his grasp on control, it didn't last much longer, the invasive muscle leaving him all together as Dr. X's hands wrapped around Senku's outer legs. 

"Come down from there, now," the command came with a tug, his mentor determined to get Senku off the counter even if it resulted in him toppling off of it. Never once feeling on balance, Senku quickly moved backwards, guided by Dr. X's hands, scoffing softly when a concerned "careful..." came from the older man. 

As soon as both of Senku's feet were on the ground his shoulders were taken and spun, turning the boy to face the taller man, his chin soon propped up to turn his gaze higher. 

"We are halfway done, " he said then, causing Senku to give a hard and slow blink up at the man. Halfway done with  _ what _ , embarrassing the hell out of him? His face was dangerously close to his mentor's, breath hitting his cheeks and lips, but Senku still had enough coherence to refuse to kiss a mouth that had just been tongue deep in -  _ actually _ , he didn't even want to  _ think  _ about it, although the thought of it still caused his dick to twitch in a desperate attempt to call attention to itself. 

Senku watched then as his mentor's stare took another dark turn, darkened eyes twisting as he flashed a smirk. "I need you on your  _ knees, _ Senku." 

Oh.  _ oh _ . Senku's top half felt way too hot once again, knowing full well his face was growing more red, if that was even possible with how flushed his entire body was at that point. The hand on his chin was released, allowing Senku to look down at where their hips pressed against each other. With Dr. X being taller, it meant his cock pressed tenderly against Senku's stomach, sliding against his belly button. 

"Do you think you can't do it?" Dr. X stepped away a small bit, giving Senku more room, but also making the boy realize he had been stalling. 

Senku could only sneer back up at Dr. X, "don't start thinking I'm dumb enough to  _ not  _ see what you're doing." He looked back down then, eyebrows furrowed low. It was working, though, despite Senku seeing right through his mentors jeering. He didn't want to look scared, not when Senku had mentioned many times in the past that he would gladly and eagerly suck his mentors cock - but that was always jests on the phone to get the older scientist riled up and actually join him in late night fun.

Senku slowly began to lower himself, his knees now sore against the tile flooring. They'd be bruised after this, he could feel that already. Luckily his view easily distracted him from any pain, his mentors cock directly in front of him, nearly touching his nose. It was actually there - not just a quick fantasy or vision that he played out, but actually right in front of him, radiating heat and a small bead of pre at the tip. 

Shuffling his knees just a bit closer, Senku reached up to take the length into his hand, his other gripping onto the rim of his mentor's pants to balance himself. It was thick and hot against his palm, his fingers curling around to turn his hold more tight, slowly starting to pump his hand. It was hard to not begin to study the organ in his hand, his brain hardwired to overthink and commit to memory anything he held. Even the skin moved differently from his own cock, a lot less loose, the difference between cut and uncut. Senku could even make out the slightest line of a scar, from past circumcision, his hand slowly moving back and forth over it, thumb pressing against the pre escaping from the tip. 

Wait -  _ right, _ this was about making him...  _ wetter. _ Senku took a deep breath, eyeing the size of it. It wasn't anything absolutely terrifying, but it wasn't as if Senku had explicit experience to prepare him, either. Mostly just very occasional porn, and his own fantasies. Quickly licking his lips to wet them as well, Senku brought his face closer, eyes closing as he laid his tongue against the hot head of his mentor's cock. There wasn't enough pre at that point to register much of a taste aside from skin and sweat, allowing Senku to focus on his actual job. He closed his mouth around the tip, his tongue rocking against it, eyebrows furrowed as he worked more of the length into his mouth before backing off again, breathing deep. 

Okay - it was too big to actually entirely fit into his mouth without hitting his throat, and Senku had no intention on gagging on his mentor's cock. It would be fine, though, the intention here was to essentially lube him up enough, Senku switching his attention to running his tongue along the bottom side of the length, intentionally bringing his tongue back in multiple times to ensure it was always wet with as much saliva as he could physically make. His hand continued to pump slowly, aiding in spreading what spit he could muster up, the pace becoming slicker and easier to keep up. Senku still did his best to bring the cock into his mouth as often as he could, more-so enjoying the way he could feel it twitch against his tongue, pre causing a bitter and sharp taste at the back of his mouth but not finding the energy or right state of mind to care about that at all. 

The only thing Senku really had going for him was knowing the things he liked himself, knowing full well that his mentor must be feeling amazing as his tongue flicked against the slit of his cock. He had to have been doing well - a hand soon coming down to run itself through his hair, wordlessly praising him. Senku's own cock bounced between his legs at the thought of it, pushing the courage into him to glance up at Dr. X. 

Their eyes locked, Senku knowing full well that it must be quite the erotic sight fro his mentor, but his own view was just as good. Dr. X had one hand locked in Senku's hair, the other bracing against the bathroom counter, staring down with those dark eyes, mouth slightly agape, hair starting to lose its perfect slicked-back style and falling into his face. It actually caused a small hum to leave Senku, closing his eyes again as he turned his focus back to his job at hand, a smirk pulling at his lips. Sure, he probably wasn't giving the best blow job in the world, but his confidence still couldn't help but be boosted a bit. 

The hand in his hair continued to pet softly before turning into a slight grip. Senku didn't mind, only taking it as a sign of a good job, pushing deeper on his mentor's cock before backing off. He was pretty much as lubed as he was going to get, with spit at least. The grip in Senku's hair started to tug harder then, the length being pressed deeper into his mouth. A smirk tugged again at Senku's lips, witnessing the quick moment of control being lost by his mentor. It was cute, in a way, feeling his cock slowly be pushed on its own, deep into his mouth. Maybe too deep. 

Actually it was  _ very  _ deep, Senku's hands suddenly bracing on his mentor's thighs, brows furrowed as his mouth was forced wider. There were two hands on his head now, keeping him firmly in place, panic only fully starting to set in as he could feel the tip of the cock press past the back of his tongue, only threatening to go deeper. His body's first reaction was to cough around the length, nose breathing in deep before his air supply was entirely cut off. He could feel the front of his nose pressing against Dr. X's groin, tickled by the mess of hair there, knuckles turning white as he began to grip and tug at his mentor's clothing. Choke - it was really all he could do, coughing again as air desperately tried to leave his lungs, the urge to gag and possibly worse rising in his throat, arms beginning to push against Dr. X's form as the older man softly hushed and rubbed his fingers against Senku's scalp. 

It ended as soon as Dr. X's hands let go of Senku's hair, allowing Senku to rip his head away, arching over into his hand as he began to suck in air, still coughing and clearing his throat and airways. Once Senku could breathe properly again he shot a dark scowl up to Dr. X, arm wiping away at the sticky mess that covered his lips and chin. 

"Was that  _ really  _ fucking necessary?" Senku questioned, his glare only deepening when Dr. X grinned back at him. A hand reached down to him, Dr. X's thumb pressing gently against Senku's bottom lip. 

"I am only just now learning your face, Senku," he said, thumb pressing in to rest against Senku's bottom teeth, his fingers curling under his chin. "I could easily fuck your throat, watch and study your beautiful expressions as you softly cry and choke," there was a tug now, upwards, forcing Senku's head high and making the boy scramble against the floor and grabbing onto the counter behind him to quickly stand. "But, coming down your throat would be a waste, at least when we have so little time..." 

Senku could only glare, ripping his mouth away from Dr. X's grasp, entirely unsure how to respond to comments like that. Idiot. He could have warned him, or at least discussed some sort of safe word with him so that he wouldn't panic with a dick down his throat. 

Dr. X's face loomed closer, poking teasingly at Senku's cheek, "My comments seem to have upset you. Do you not like that? Me, calling you beautiful," his hands clasped around Senku's face, palms holding it in place as he moved their lips close enough to barely touch, "such a pretty boy with a willing mouth." 

Their mouths met, Dr. X's tongue hungrily invading Senku's with little hesitation, running along the roof of his mouth and teeth. Senku squirmed a bit against the kiss, unsure why the hell this man would be so eager to taste his own dick, but the thought of where his mentor's tongue had been sped to the front of his mind, only making it feel more intense. But there was no pulling away, Senku's back being pushed against the counter now, his face still being held in place as his mouth was completely dominated by the older man. Teeth grazed at his lip, filling Senku with the need to bite back, but his mentor was pulling away before Senku could grasp at the chance. 

"Turn around," his tone was low and deep, something about the order making a chill run up Senku's spine. 

He hesitated only for a moment before listening, twisting in his mentor's gasp as he faced the mirror once more. It was still dripping with condensation and fog, but Senku could still easily make out his body and face, flushed and hair falling everywhere. But his view quickly changed, a hand on his back pushing him down, elbows hitting the hard counter top. His cheeks were being pulled apart again, the feeling of his mentor's cock slowly sliding against his crack making Senku's body become rigid. This was happening - ten billion percent, they were there and it was actually happening. 

"You know," Senku spoke, resting his chin on his arms, peering back at his mentor and desperate to regain a bit of control, "everything you did before is pretty useless." 

His words didn't stop Dr. X from slowly pressing the tip of his dick against Senku's hole, not at all putting enough pressure to enter but still sliding against the sensitive skin there. "Is that so?" 

Senku grimaced, gulping down his nerves, his knees feeling sore and shaky beneath him. "Y-yeah, I mean. Saliva evaporates faster than even water." 

"Uh huh," Dr. X nodded along slowly, not even looking at Senku's grin. "You're right. I wonder, then, why I did all that, if you're already in need of being lubed up again." 

Senku had half a mind to nod in triumph, but stopped, turning his stare forward. Damn it. All of this was just a reason to get Senku riled up, to tease him and make him squirm. He pushed his forehead against his arms, hiding his face between them. Dr. X had controlled every single element of this. Senku wouldn't be surprised if his mentor had everything meretriciously planned out since the second he heard of his arrival at NASA. And, somehow, Senku went along with every step. 

The sudden pressure behind him shot Senku's mind back into the present, his mentor's cock slowly pushing past his barriers and filling him. Senku did his best to relax, breathing out deep, wincing all to himself as he continued to hide his face in his arms. There was no way they actually prepared enough for this, Dr. X's cock much bigger than just two fingers, stretching Senku to a limit he had never even done to himself before. He felt a hand against the small of his back, pressing down slowly, massaging in gentle circles as small shushing noises came from behind him. It was soothing, in a way, at least enough to let Senku relax his muscles as the length pushed deeper into him. He could soon feel Dr. X's hips pressing against his ass, telling him that he at least was able to take it fully, dick twitching eagerly below him. A sigh came from behind him now, registering as shaky and deep - did it feel that good to be inside him...? For Senku, it only felt a bit odd. Invasive, too full, weird. 

His hips swayed backwards as his mentor exited him, only to then be filled to the base once more. It started a pace, slow at first, the hand on Senku's lower back not leaving. Each push forward caused Senku's dick to press against the counter, bouncing slowly and then more erratically as Dr. X's thrusts finally began to pick up speed. The smacking - somehow that noise was the most embarrassing one, Senku's ears full of the sound of their bodies hitting one another. It at least drowned out the sound of his own noises, gritting his teeth as small moans began to fall from him. 

His body was growing more accustomed to the length inside him, Senku's back soon arching upward as he balanced himself on his elbows. He was losing the ability to care much about how he looked, his mouth beginning to hang open as he felt his mentor's fingers slowly ghost up his spine. It was finally, really starting to feel good, Senku having to continuously clench his jaw in an attempt to not call out. 

The pace came to a quick and sudden stop, Dr. X pulling from Senku's body entirely. It gave Senku the strange sensation of feeling empty, a thought he had no real time to focus on as his form was quickly being moved by his mentor, spun around once again to face him. 

"Up," the order came with a quick tug at his waist, Senku not having to be told twice to hastily raise himself up onto the counter, which was now warm against his skin. Dr. X wasted no time in bringing their bodies close again, arms hooking beneath Senku's legs to raise his knees high. 

It wasn't a new view, but something about it was different, Senku watching his mentor's focused gaze. The concentration on his face, the flush on his own cheeks now, slightly pink, sweat dripping down furrowed brows. It was intimate, being able to see him this close, to see the way that his body was becoming lost to it all. Despite how in-control Dr. X was acting, he was also feeling good. Senku's confidence soared a bit higher again from the sight. 

He watched then as his mentor slowly spat onto his fingers, pressing it low and against Senku's hole. Despite how embarrassing a sight it was, Senku couldn't help but smirk. "Told you saliva evaporates too quickly." 

He got only a cheeky grin in return, Dr. X holding his hips tightly in place as he gave a sudden thrust forward, Senku's body happily taking in the full length in one shot. It caused him to jolt, choking out a noise as his hands desperately dug into Dr. X's shirt. He swore softly in his own language, knowing full well that the tone of it would still register as a curse to his mentor. 

Dr. X gave a low chuckle now, pushing Senku's legs wide, making Senku's hips roll more forward. "This position should be much better for you in the end, Senku," he said while licking across Senku's cheek, collecting the tears that had welled up there. "Try not to make too much noise." 

There was no wasted time on slow paces now, Dr. X quickly returning to where he had left off, his mouth finding Senku's as his arms wrapped around the younger boy's form. Senku followed in suit, his hands desperately wrapping high around his mentor's neck, filling themselves with his hair, not a fear inside him telling him not to tug and pull. Dr. X didn't seem to mind it at all, giving deep growls into Senku's neck, teeth sliding along his moistened skin. The thrusts seemed slicker now - maybe from the spit, maybe from pre, Senku didn't know nor did he find himself caring, every now and again feeling a jolt from deep inside him. Dr. X was right - this position was a lot better, allowing the thrusts inside him to occasionally rock against his prostate, each time making his thighs quake, his cock weeping and bouncing happily against his stomach. 

Senku found himself becoming lost to it, his face cradled deeply into his mentor's neck, not even caring if noises were coming from him. They must have been, with how fast his breathing was. But, Dr. X was slowing now, bringing Senku back to the real world for only a moment, enough of a moment to hear a sudden commotion outside the bathroom door. 

His body froze, hands falling to Dr. X's shoulders and fists full of fabric. Dr. X stopped as well, his gaze turning to the door, back straightening up as he listened. The door was locked - it would be fine. Even if someone came knocking on it, his mentor could just simply say that the bathroom was occupied, right?

"Why are you stopping...? Senku asked, looking up to his mentor with a growing grin. "Think someone is going to barge in through a locked door?" Dr. X slowly looked back at him, an eyebrow cocked high, but Senku continued, tugging now on his mentor's shirt to bring him closer again, "Or, are you going to pull out right before you finish and claim you have an important meeting to get to?" 

Dr. X's expression turned bright again, his own smile growing. He gave a delighted hum, nails deep in Senku's thighs as he gave a sudden and deep thrust back into him, eyes creasing into a wide smile as Senku's body tensed around him. "Senku, what a roundabout way of begging me to come inside you." 

Senku glared in return, working hard to keep up his cocky grin. Of course he had a good comeback. The murmuring outside was growing more distant, most likely a pair of NASA colleagues walking through the halls on their way to a different part of the building. 

Dr. X began to bite at Senku's bottom lip, pulling back out slowly only to give another hard and deep thrust forward. "I wonder... if I will hear rumors, soon. Gossip of someone being fucked in the bottom floor bathroom." The heavy thrusts turned into a rhythm all their own, Dr. X's mouth engulfing Senku's neck once more, sucking again on marks that were already bruising. 

Senku gave a low curse, eyes closing as his body happily accepted each thrust. He couldn't care about rumors - as long as they didn't come back to him, and seeing as he would be back on a plane in just a few hours the chances of him being wrapped up in gossip was slim. But the idea was something that only set electricity to his nerves. Maybe those people  _ did  _ hear. Maybe they were talking about it in excitedly hushed whispers. Fuck, why was that actually  _ hot _ ?

Dr. X slowly brushed his lips across Senku's cheek, "touch yourself, Senku." It was such a simple command, but the way his voice reverberated through Senku's body caused a shaky moan to fall from him. Senku's hand reached down between their bodies, wrapping around his cock and wasting no time in turning his grip tight and pace fast, matching the thrusts his mentor was rocking against him. Each grind brought not only that shameful slapping noise to Senku's ears, but another jolt deep inside of him, Dr. X's cock so easily colliding against his prostate. 

Once more, their mouths were together, Senku's mind too lost to even bother trying to match his mentor's enthusiastic tongue, moaning deep as his body was beginning to tense. He was close - the anticipation and fear of Dr. X suddenly stopping pushing Senku's pace to erratically speed up, legs moving to clasps around the older man's hips. It caused Dr. X to chuckle into the kiss, but Senku could care less, his hips now beginning to twist and grind back against his mentor's movements. 

The kiss began to break, hot breath against Senku's mouth. "Do you need to come?" It was a question, but Senku could barely register it, mouth wide open and gasping out a series of moans. He could feel his mentor's forehead against his own, slick with sweat, his voice a low husky whisper, "you can come, Senku. Let me finally see how cute your face is..." 

A whimper left the boy, both of his cheeks being held in place by Dr. X's hands as their bodies continued to rock. There was no room left in Senku's brain for shame, the grip on his cock turning tight as his peak finally hit, trying hard to grit his teeth but gasping out as his body began to spasm, clenching around the cock inside him. He knew his mentor was watching his face, he knew he was making noises, but nothing else in his body was even bothering to register such things, only rocking along to his orgasm as the grip on his cock slowly milked each long string of cum from him. He could hear the slightest grunt from Dr. X, the idea of his mentor's cock being squeezed inside him only causing more cries to leave his throat. 

Dr. X didn't slow at all, bringing Senku to a new sort of edge, his body and mind used to being able to cease all movement and stimulation as soon as he came. There was something raw about it now, Senku still in a bliss of feeling amazing but all of his senses slowly coming back to him. The hand that held his cock was pushed aside now, Dr. X taking the overly sensitive organ into his hand, rubbing his thumb softly across the tip. Senku's legs quickly began to shake in response, gasping deep and his entire stomach sucking in and quivering as his body tried to wiggle away from the over-stimulation, unable to control the erratic cries that left him. 

"There we go..." Dr. X slowly spoke, his lips pressed against Senku's temple, burying himself deep. Senku was able to  _ feel  _ it, an entirely new sensation, hot and wet inside him. Nails were digging into his skin again, across his back and hips, causing more marks Senku would have to hide for awhile. His mind was returning, fog beginning to leave, allowing Senku to really focus on the small noises that were leaving Dr. X's body, his own low moans and shuddering breaths. Senku couldn't help but reach upward, cupping both of his mentors cheeks as he tugged the older man down for a lazy kiss, both of them still desperate for breath. 

Their bodies were still now, aside from Dr. X slowly leaving a soft trail of kisses along Senku's bottom lip and chin. Senku's body was allowed to fall limp now, legs no longer wrapped high around the body in front of him, thighs still giving occasional tremors as his body calmed down from such a high. 

A shudder left him as Dr. X finally pulled out, followed by a wet warmth leaving Senku's body that he couldn't find the energy to be worried over. He leaned back then, back hitting the cold mirror, watching as his mentor quickly regained his own composure, or at least a lot more quicker than Senku could bother to gather his own. He moved around effortlessly, walking to the sink right beside them, running his hands beneath the warm water and cleaning himself off. It didn't take long at all before he was fixing his hair, pants and belt already done back up and clothing being buttoned. 

Was there nothing to say? Senku's brows twitched downwards, watching now as Dr. X secured his long black lab coat around his body, redoing all of his collars and his tie. 

"Are you only going to watch?" Dr. X asked then, nodding towards Senku's own clothing pile. "I am sure your father is frantically looking for you." 

"Ah-" Oh. Damn, right. Senku's mind was finally reaching back to it's more normal running capacity, sitting forward as he reached over for his pants, digging into it for his phone. If his dad was worried he could just say he got a bit lost wandering around the space center. 

Dr. X's form was in front of him again, causing Senku to look up at the dark figure. 

"Open up," it came with a tug to Senku's jawline, Senku unable to deny it at all as his mouth was forced open. Something thin and slightly sharp against the corners of his lips was forced into his mouth, Dr. X pushing his jaws closed and teeth to clasp around it. 

The damn credit card, Senku could tell what it was from the feel of the raised numbers against his tongue. He threw a glare back up at the man, ripping it from his mouth. Dr. X only smiled sweetly back to him, walking now towards the bathroom door. As soon as his hands began to fall on the door handle, Senku's phone filled the small room with the echoes of an incoming call, vibrating against his fingers. 

"It seems we both have places to be," Dr. X said then, unlocking the door and causing Senku to suddenly become  _ very aware _ of how naked he was. 

He ignored his phone entirely, dropping it onto the counter as he pulled at his shirt and pants, stopping suddenly as he saw the streaks of cum dripping both off him and  _ from  _ him. Damn it. He'd have to clean up first. 

But Dr. X wasn't waiting, a click signaling the unlocking of the door, pulling it open but thankfully standing in front of the door crack, giving Senku at least a bit of privacy. 

"You may want to lock the door once I leave," his smile was all too nice, making Senku scowl back in return. Before Senku could throw snark back his way, the door was being pulled wide open, Senku covering his body with his shirt despite the mess on his chest. "Ah, Senku," Dr. X said then, turning from him but keeping the door wide open. "Next time you visit, a warning would be nice." 

He walked out after that, the door slowly closing, a click sounding out as the latch hooked. Senku quickly slid himself from the counter then, legs feeling weak beneath him, bracing himself against the sink countertop as he scrambled to the bathroom door. Hearing the lock click between his fingers brought back a sense of safety, a deep sigh leaving his body. 

His cell phone was ringing again, but he could let it fall to voicemail one more time. At the sink, Senku began to let warm water rush over his fingers, catching a glimpse of himself in the mirror, only looking more disheveled than before. His gaze then fell to the credit card on the counter next to his vibrating phone. 

A soft groan left him. He basically just sold himself out for a bunch of money. Though, even if Dr. X hadn't waved the credit card in his face, the odds of him following his mentor was still pretty high. Senku grabbed the card, running his thumb over the numbers and name etched on the top. This was just to make Senku focus on the fact that he got money for sex. A reason to tease him later, something to bring it up and rub it in his face and try to shame him. 

Fine. He could deal with that, if he knew it was coming. He could let Dr. X have his fun. 

But in the meantime, Senku was going to spend every last penny he could get.

* * *

**Notes for the Chapter:**

> ; w; that was fun
> 
> You can find me on twitter over [HERE](https://twitter.com/SewerThot)
> 
> Also also: If you like this ship and others like it, consider joining the Dr. Stone Shipping server. All ships are welcome!  
> There's lots of events, RPs, headcanons, and just fun talks about the show and all your faves ;)  
> If you're curious, come check it out!  
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**Author's Note:**

> ;) 
> 
> You can find me on twitter over [Here!](https://twitter.com/SewerThot)


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